Lillie Cotgrove, 13, was "devastated" when her best pal Lily Wythe, 14, was diagnosed four months ago with the deadliest type of childhood cancer.
The survival prognosis for Lily's condition - a high-grade diffuse intrinsic pontine glioma (DIPG) - is just eight to 12 months.
Wythe family / SWNS
So when Lily's parents found "promising" clinical trials for her cancerous brain tumor in Seattle, Lillie was determined to do what she could to help her friend.
Schoolgirl Lillie squealed with delight as her fundraising page, The One Pound Warriors, reached its £300,000 target - just a week after she created it on Facebook.
Paul Davey / SWNS
The One Pound Warriors - which asks for a voluntary £1 donation from all its members - has received a host of celebrity endorsements including Jonathan Ross, Rachel Riley, and Gemma Collins.
The Facebook page was set up by Lillie and her mum Sarah last Thursday (January 16), and its 134,000 members have helped to raise £230,000 (~$300,000) in just seven days.
This total was added to £78,000 (~$100,000) raised by a separate GoFundMe page, which was set up nine weeks ago in November 2019.
And when Lillie was told that her fundraising page had reached its target, she squealed with excitement, before hugging dad Mark and becoming visibly emotional.
Paul Davey / SWNS
Speaking from her home in Benfleet, Essex, England, Lillie said:
"It's absolutely incredible what's been achieved. I did this because I really wanted to help Lily, and at the start I felt a bit like I couldn't help her."
"But then I set up the Facebook page, and lots of people started helping, and now, we're going to get Lily to the U.S. to get a clinical trial done," she added.
And her proud dad Mark, beaming at his daughter's achievement, said:
"It's just incredible, really. I couldn't be prouder of my daughter.
"All of this was borne out of the helplessness of the situation, and wanting to help her dear friend - and look what's been achieved. She's going to get out there to Seattle. It's amazing."
Wythe family / SWNS
Lillie also added her thanks to national charity Brain Tumor Research, who have helped the two girls spread the word about The One Pound Warriors.
"Brain Tumor Research has helped us so much," said Lillie.
And Lily's emotional mom Diana Wythe said:
"Lily and I never imagined we would manage to raise the £300,000, or that it would happen so quickly. Lily is blown away by it all."
"We can't believe there are so many people out there who have been touched by Lily, with people giving away precious savings or even their wages and children their pocket money."
"I want people to rest assured that any donations not needed for Lily, will be given to charity. We aren't making any money out of this."
Diana added:
"Lily had a scan on Sunday and we will get the results next week, which can then be sent to Seattle Children's Hospital to find out what the next move is. This has happened so quickly, we haven't even had the chance to get our visas ready, so that needs to happen fast."
Paul Davey / SWNS
Lillie's fundraising efforts for her friend have touched people's hearts around the world, with many members of The One Pound Warriors nominating her for a Pride of Britain Award.
The parents of both teenagers have been overwhelmed by the "phenomenal" response, which has included retweets and messages from British celebrities including Jonathan Ross, Gemma Collins, and Keith Lemon.
Jonathan Ross shared the fundraising page on Saturday to his five million Twitter followers, writing:
"If any of you feel like joining me in chipping in I know it would be appreciated."
Wythe family / SWNS
And Gemma Collins shared the page on Sunday to her 1.3 million followers, writing:
"Have a read, share and donate if you can."
Hugh Adams, head of stakeholder relations at Brain Tumor Research, said:
"This is the most extraordinary achievement. Huge congratulations to Lillie and everyone who has got involved with The One Pound Warriors."
"Our hearts go out to the family of Lily Wythe as they start preparing for further treatment which they had been told by doctors in the UK wasn't possible. It is just not acceptable that families who have loved ones affected by brain tumors are sent home and told to make memories."
"On behalf of us all at Brain Tumor Research, I would like to wish Lily and her family all the very best," he added.
Paul Davey / SWNS