A teenager who helped raise £300,000 for her best friend's brain tumour treatment has described her death as "extremely sad".
Lily Wythe, 14, from Essex, died on Sunday following a "huge seizure", her family said.
Her best friend Lillie Cotgrove set up an online campaign called One Pound Warriors to raise funds for medical treatment in Seattle, US.
Lillie said she would miss her "amazing" friend "so much".
Lily was diagnosed with an inoperable diffuse intrinsic pontine glioma (DIPG) brain tumour in September.
In January, 13-year-old Lillie set up the One Pound Warriors Facebook group which asked members to donate £1 each in order to raise funds for Lily to be treated at Seattle Children's Hospital in the US.
Celebrities including Countdown's Rachel Riley and The Only Way Is Essex's Gemma Collins publicly supported the campaign.
The target of £300,000 was reached, but Lily died before she could travel to Seattle.
In a statement, Lillie said: "It makes me so sad that the treatment we raised the money for isn't available in this country and there are no clinical trials currently for her DIPG brain cancer in the UK, which means finding a lot of money to go to abroad - something most families cannot afford.
"I am extremely sad to see Lily leave this world and we all love her and will miss her so much.
"She will be forever in our hearts as our brave warrior and I'm pleased that so many people saw how amazing and brave she was."
Lillie said the One Pound Warriors campaign would continue to help other children.
"We are also working with Brain Tumour Research because we want trials in this country and research to bring better outcomes for brain tumour patients," she said.
"I want this to be Lily's legacy."