Hannah Jones, 13, who said she wanted to die with dignity, has been told she can travel to America with her parents and three siblings after an insurance company came forward to provide cover.
Her family had feared her "dream" of visiting the Disney resort had been crushed when attempts to secure medical insurance were refused.
But she was "delighted" when an anonymous British insurance company agreed to provide cover, worth an estimated £5million.
At her home in Marden, Herefordshire, she said: "I am overwhelmed. I absolutely love Disney and watch all of the films. To be able to go and see them is a dream come true.
"The week away from our routine of doctors' appointments and hospitals will be a wonderful distraction for us. We will feel like a normal family for a while."
Hannah's father Andrew Jones said: "I can't thank everyone who has offered to help enough. Our main aim was to find someone who could insure our little girl for her dream holiday. My wife and I are thrilled that we have been able to do this and now we cannot wait to see the smile on her face."
Hannah, who suffered heart failure as a result of treatment for leukaemia, will be one of 40 children flying to Orlando, accompanied by a team of paramedics and doctors, with the charity, Caudwell Children, on Dec 1.
Herefordshire Primary Care Trust (PCT) dropped a High Court case after a child protection officer said Hannah was adamant she did not want surgery.
Trudi Beswick, chief executive officer of Caudwell Children, said the charity had been inundated with calls offering help.