She'll Do It Regardless

Honestly, I'd say she already had a guy lined up and if you adamantly say no she will do it regardless. I am usually hopeful on this subject, but this sounds like she wants to have her cake and eat it too. Like she wants to be in a steady relationship and still play around while she's young. I'd say just leave now, she won't admit she has a guy on the mind but will shortly after you agree.

- Kumbackkid

Different Boundaries

If you don't want your girlfriend to have sex with another guy, you shouldn't have had sex with another girl.

IMHO you've screwed up. You overstepped a boundary that you implement on her. How can you have a good relationship if the other is treated unequally and has different boundaries?

I would always put myself into my partners position before I'd do something like this.

Also did she want you to have that threesome, so it would give her leeway to do it with another guy?

- tomputer

Retroactively Insecure

Honestly, it sounds like she is retroactively insecure that she saw you with another woman so she feels like the only way she'll feel okay inside is to do the same. Really you should ask if this is about her feeling insecure/jealous more than if it has anything to really do with fucking another guy.

- 0909a0909

We Need To Talk

"Have a seat. We need to talk. I am really not happy with how things went down after our threesome. I feel a lot like you set that up because you want to have sex with another guy and that you have some one in mind in particular. It feels like you initiated this to try to manipulate me into saying yes to this situation, and I'm pretty pissed off about that. Now I also have the concern that no matter what I say, you're going to go cheat anyway and try to justify it to yourself. You've put up enough of a fuss about this that I really don't feel like I can trust you to stay faithful to the boundaries of our relationship. It's to the point where I'm thinking of ending things altogether, but before I go that route I wanted to give you a chance to say anything you feel that you need to."

At that point, you're watching for her reaction. If she continues to try to justify and convince you, proceed with the dumping. Very importantly though, if she back pedals and tries to save the relationship, you absolutely need to pin her down on who it was she had in mind. Even if it was several some one's, I'd probably insist that she cut contact with all of them as a condition of moving on together. She is no longer interested in their friendship platonicly and you would be completely justified in cutting persistent threats out of your relationship. You avoid cheating by not placing yourself face first in the middle of temptation, and you're honestly never going to be comfortable with her hanging around them from that point forward. While you're on the precipice of ending things anyway, don't allow the future to be set up in a way that's going to have you riddled with anxiety. Get what you need full bore from this conversation or find some one who can respect your boundaries more than she does.

- Falxen

It's A Wildcard

Having had threesomes before while in a relationship, I can say that it's the kind of thing that you just can't plan for. Even if you have the strongest relationship in the world and both of you seem completely on board and there are no ulterior motives, you never know what might change when you're in the middle of things.

My last ex ultimately ended up cheating on me about six months after we had a threesome with one of her friends. She told me post-breakup that she really had gone into the threesome all excited and ready (it was her idea), but that she couldn't get the image of her friend giving me oral out of her mind afterwards. That was pretty much the only thing that night that she wasn't directly involved in, and only for a period of about a minute or two, but she said that image overwhelmed all of the good experiences for her. I think a desire to "even the score" prompted her cheating, and while I'm sure your girlfriend is a better person than my ex, I just have to reiterate: threesomes are wildcards. Even with the best possible preparations and situation, you still never know what the fallout will be like, especially if it's your first time.

- AngryPurpleTeddyBear

Different Mentalities

This issue you're talking about is a big reason why I'm (f) not into the idea of a threesome. Because between my boyfriend and I, I would be down to do MFF or MMF, but he would only want MFF. What that tells me is that he doesn't actually believe pleasure should be shared and we shouldn't be tied sexually to one person.

Rather he's just cool with a threesome because he doesn't see a girl joining as a threat. So we would be doing a threesome based on different mentalities, which seems way too risky and like it wouldn't be fair.

- GrandadsLadyFriend

Learning An Important Lesson About Yourself

If you're not comfortable with her f^cking another male-identified and penis-equipped individual in any capacity, under any circumstance, then the relationship is over. If you say no, she's going to do it anyway because by her logic, you fucked another woman.

If you are, then take a few days to envision a scenario you'd be comfortable with. Maybe she just goes out one night and does her thing, without you knowing anything. Maybe you're fist-bumping your bro as you hook him up with some quality trim. Whatever. Write it down, think it out, and tell her what you're comfortable with. After all, the first threesome went down as she proscribed, right? Get it done, and see how you feel. If you're super skeeved then it wasn't meant to be and you've learned an important lesson about yourself.

She wants to do it without ending your relationship. That's worth noting.

- bostick

Long-Distance Camping

I enjoy them a lot--but you have to be damn careful the first few times. You have to be really communicative before and during the event, you have to slow it down or stop entirely if anyone is having any problems, and you have to stick fast to the boundaries laid out before everything gets going, no matter how much you think it's okay to go past them because she's having a good time. Like, if she says "No an*l with the other woman," even if she says "Go ahead and do an*l" during the thing, DON'T DO IT, because afterward she might think "Yeah, that was stupid of me, I wish I hadn't given him the go-ahead." Passionate decisions are frequently hurtful decisions, and I think that causes as much trouble as any other part of a threesome could.

It's a lot like...long-distance camping, I guess? For the people who do it regularly, who are accustomed to all the work that goes into it, it's not that difficult, and generally it only gets easier with time. For the people who are completely new at it, there's a couple of different types--the ones who do all the reading, lots of prep, think carefully about "What would I do if (bad situation) happened?" set milestones where they'll check in, and make sure before and during that their companions are all on the same page.

And then you get the ones who go in completely inexperienced but thinking "This isn't a big deal! I don't need to tell anyone what's going on. I don't need to make sure I've prepared, it's not like it's going to be that much different than what I've done before."

But a threesome is not like a two-person overnight! And unfortunately there's no such thing as park rangers or search and rescue for sex...

- RememberKoomValley

A Little Introspetion

Ultimately, if you aren't comfortable with a MMF threesome, there isn't anything wrong with that. There are a few things you may want to consider, which could impact what happens from here or just be good introspection.

-You aren't OK with her having sex with another man, but you were OK with her having sex with a woman. Why is that?

-Why do you assume that she's the sort of person who would deliberately manipulate you like this, instead of thinking the most likely scenario was that the urge for a MMF threeway came after she fulfilled her fantasy of a FFM one and experimented with that woman? Has she behaved in ways before that indicated she's a manipulative person? If so, this could have been the latest red flag. If not, consider why that's what you think of her and why you jump to that assumption first.

-If you're happy with a sexually adventurous girlfriend, and end up staying with this one, why don't you think of some things you'd like to experiment with and bring them up to her as well? She may be feeling like it's all up to her to spice up your sex life and that's why she got a little stuck on this.

-Have a conversation with her about how relationships aren't about being "even", they're about being "happy". Bringing a woman into the bedroom made you both happy. Bringing a male in only makes her happy. The ideal solution isn't a tally system of getting what each of you wants - it's finding things you both want and enjoying them together.

-Don't bother with the manipulation tactics people have suggested here. If she was in fact being a manipulative person with this, it brings you down to her level. If she wasn't, then it makes you the manipulative ass in this situation. There is not a "win" condition possible in that scenario.

- Reddit

Jumping To Conclusions

I'm going to be honest: I don't see the girlfriend as immediately wanting to cheat. He should NEVER do something he doesn't want to, and his girl is wrong in trying to pull the "you got to f^ck another girl, now I do" card. However, immediately jumping to the conclusion that she's already emotionally invested in another guy is... Jumping to conclusions. If and only IF you're actually open to a threesome with a guy, then insist that you'll be the one picking the guy. Or insist that your both pick a guy TOGETHER. That should alleviate some of your worries. Don't try to make it a petty revenge and purposely pick a guy she would be totally turned off by though, just to make sure that it's truly a fun time.

There's still a possibility that she simply went about the VERY wrong way. She's still very wrong for trying to guilt you into having a threesome with a guy if you're truly not into it, but I think that doesn't immediately mean she wants to cheat on you. Honestly I'm pretty interested in threesomes with all sexes myself, and I can see myself saying "hey, what do you say about trying ___ out next?"

That wasn't what your girl did and it's really too bad, but it's possible that the sentiment behind it was similar?

- magikarpcandosplash

Establish Dominance With Uber Gay Sex

I have two things I would do. Ask her if she has chosen a guy or if you could chose a guy since she chose the girl. This lets you know if she had this planned all along.

Once you 3 are all alone it would be the perfect time to say "shotgun" and get first dibs. Have uber gay sex with the guy and make her sit there as you have having it while keeping stern eye contact with her. Once you guys are spent, just collapse in to a huddle and fall asleep with a grin on your face.

- DarkCircle

Different Meanings

It's possible you both thought that the threesome meant different things. So, you thought it was a one-off and she thought "Okay, so we're trying option 1 and next time we'll try option 2."

She thus might think its unfair because she expected that, but that doesn't mean that bending to that would be fair to you.

Obviously, you shouldn't have to do anything sexually that you don't want to, ever. I just wanted to put that out there.

- wafflesthewonderhurs

Why Is She Being Demonized?

Haha wow. So if a girl wants a MFF threesome with her boyfriend, it's all cool, but if she also wants a MFM threesome, it's obvious that she's shady and just looking for an excuse to cheat? It's totally not possible that she's just interested in the other kind of threesome, and was using the "fairness" argument as a weak tactic to try and convince OP. Like seriously, just as much chance that the first threesome was "an excuse to cheat" too... except dude was ok with that one.

There is zero indication that if he says no that she's gonna go do it anyway. I'm sick of the knee jerk reaction people here have to any woman who suggests a "devil's threesome." Why do we even call it that? That's so stupid. Do all guys who want a MFF threesome already have a woman picked out too? Is that why you're so suspicious? Why is expressing a desire to do one type of threesome an indication that a girl is planning to cheat, while the desire for the other kind is normal?

OP, don't do it if you're not comfortable with it, but don't dump your gf over it either. Recognize that she probably did do the original threesome more for your pleasure than hers. Honestly, if the situation were reversed, and the MFM threesome happened first, wouldn't you also ask for the other kind? She should have been honest about wanting a MFM threesome before you had the other one, but really you'd have just been posting here a week ago and the comments would be exactly the same. "She just wants to f*** another guy, so she's gonna let you f*** another girl for leverage". Completely ignoring that you also wanted to, and did, f*** another woman. So why is she being demonized for a desire you actually acted on?

- sillypuppy215

Hypocritical

It's not that you don't want to that's hypocritical. It's that when she asked about a fmf, you were happy, and when she asked about a mfm you were pissed and suspicious. She's asking for exactly the same thing in both instances--a threesome--but one makes you decide she wants to cheat and one makes you happy. That's where the problem is. (I'm not saying you should feel guilty for saying no, I'm saying you shouldn't be pissed that she asked. That's a huge difference.)

- socksforbdays

Clearly This Is A Plot

I've read a few of the comments. I just want to say something about them. People this isn't about his girlfriend wanting to experiment or have another threesome. She asked to have a MMF threesome or f^ck a guy alone.

If it was just a "can we have a MMF threesome now" that would be fine. She specifically said she should be able to f^ck another guy because of the FMF threesome. She has already picked a guy and wants to f^ck him either in a threesome or alone. This is her manipulating the OP through the initial threesome. Clearly this is a plot that has been in the making for a long time.

- Reddit

Incompatible

First of all, yes this does seem like an underhanded move and was manipulative. She shouldn't be pressuring you into a threesome because that was never agreed upon.

Second of all, if you're that afraid of her cheating, then there isn't a lot of trust (or honesty) in this relationship and this issue is moot. You shouldn't have to agree to a threesome to keep someone from cheating. If it's that important to her to have sex with another guy, she should break up with you first.

But relationships can't be 100% about tit-for-tat and legally binding verbal contracts and whatnot. There's more questions here:

1. Who picked the girl? If both of you had a say in it, you should have a say in the guy.
2. Just to make things clear, she's not asking for a MMF (where you'd have to interact with a guy) right? Is a MFM (where the men don't interact) uncomfortable for you? Or is it just because you can't handle her being with another man at all? For threesomes it really doesn't matter if anyone is bi. It's not correct to say that a FFM is okay cause your gf is bicurious but a MFM is not because you're not bicurious (unless she's forcing you to interact with him).
3. If she really has another guy in a mind specifically she really shouldn't have been this underhanded. She should've said "hey I really want to f^ck this one guy, it's not an emotional thing at all, I won't leave you for him I just think he's hot. Can we talk about it? Would a threesome situation make you feel more comfortable since you're involved? Why don't we do a FMF to spice things up too and fulfill your desires?"

I guess you might end up saying no more threesomes or sex with anyone else for anyone. Maybe you guys are incompatible that way. She needs to understand that she should be open with her intentions and fantasies rather than trying to do something underhanded. But if it's still that important for her to have sex with another guy and you're not comfortable with that in any context (even if you get to pick the guy and are present) then I guess it's not meant to be.

Good luck!

- throwthebar

Obvious It Was A Set Up

It's so obvious it was a set up. She's been banging this guy or emotionally cheating on you with him behind your back already and now she wants to legitimise it.

Break up with her. You can't both grow through this problem together, she wants to fuck other people already and now you're the gatekeeper, something women aren't used to. Guarantee you she's going to go behind your back if you say no anyways.

- Silva_Shadow

Try Communicating

I think you might be over thinking things here. I'll try to shed the light from the opposing side. Maybe you should talk to her and see if the threesome ended up hurting her feelings. I mean, she did watch you bust a nut inside of another girl. That's not easy for any SO to watch. That's probably why she feels justified in having another man in the mix.

Also, if she wants to experiment and you were okay with another girl coming along, it shouldn't be wrong for another guy to come along. That's pretty unfair to be okay with a two girl threesome because you got the better cut than with a two guy threesome. Maybe she's watched some porn or heard about an awesome two guy threesome scenario and wants to try it out. Everything doesn't have to have an ulterior motive! Also, if that happened to be her alternative motive, that's pretty jacked and you should dump her.

"Colon pounding" some other guy in a threesome like another user posted not only would make things worse all around, but would be a pretty jackwad thing to do if she didn't intend none of that to happen. Also I think the man there would want to involve her too. Point of threesome. You should communicate with her. Most problems I see on here is lacking that HUGELY. Ask her, try to understand, and if she's twisted, she's just a girlfriend and not a wife or something. Dump her. Simple.

Sorry for any mistakes, I'm on my phone.

- guellikeafish

Open and Closed

So you guys opened up your relationship for a girl, but you're closing it again before a guy can get involved. Sounds unfair to me.

And anyway, if you don't want an open relationship like you said at the end of your post, then why the hell did you open it in the first place? If I was your girlfriend, I'd be miffed too.

- Zuccherina

Reciprocity

How have you not discussed the reciprocity factor before accepting the ffm threesome?

Considering your age, this looks to me like a future breakup and lesson learned for the future to discuss boundaries, fantasies and what is acceptable to both partners before bringing another person in your bed.

- anatem