Her divorced parents had become embroiled in a dispute relating to whether her remains should be taken to a specialist facility in the United States and cryogenically preserved.
The girl, who lived in the London area with her mother and had a rare form of cancer, had taken legal action.
She had asked a High Court judge to rule that her mother – who supported her wish to be cryogenically preserved – should be the only person allowed to make decisions about the disposal of her remains.
Mr Justice Peter Jackson had made the ruling she wanted in October – following a private hearing in the Family Division of the High Court in London - and lawyers say her remains have now been taken to the US and frozen.
The judge had said that nothing about the case could be reported while the teenager was alive, after she said media coverage would distress her.
He also ruled that no-one involved could be identified – again in line with the girl’s wishes.
She had been too ill to attend the court hearing.
The teenager had been represented by lawyers and had written to the judge explaining that she wanted a chance to “live longer”.
Mr Justice Jackson had also visited her in hospital.
The judge said he had been moved by the “valiant way” in which she had faced her “predicament”.
He said the girl’s application was the only one of its kind to have come before a court in England and Wales – and probably anywhere else.
The judge said the case was an example of new questions science posed to lawyers.
He said he had made decisions relating to a dispute between parents – not about the rights and wrongs of cryogenic preservation.
The judge said the teenager had carried out internet research into cryonics during the last months of her life.
He said there was no doubt that she had the mental capacity to launch legal action.
A lawyer representing the girl had described her as a “bright, intelligent young person”.
The judge was told that she had pursued her investigations with “determination” even though a number of people had tried to dissuade her.
Mr Justice Jackson said the relationship between the girl’s parents was “very bad”. He said the girl had lived with her mother for most of her life.
She had not had “face-to-face” contact with her father for eight years at the time of her death.
The judge said she had refused to have contact with her father, had not wanted him to have detail of her illness and had not wanted him to see her body after she died.
He said a child could not make a will - and he had been asked to decide where her best interests lay.
Mr Justice Jackson said the girl’s mother supported her wishes for cryogenic preservation.
But her father had been reluctant to approve the plan.
He had been concerned about consequences of his daughter being cryogenically preserved, and had been concerned about the costs involved.
“Even if the treatment is successful and she is brought back to life in, let’s say, 200 years, she may not find any relative and she might not remember things,” he had told Mr Justice Jackson.
“She may be left in a desperate situation - given that she is still only 14-years-old - and will be in the United States of America.”
But during the litigation his position had changed and he later added: “I respect the decisions she is making. This is the last and only thing she has asked from me.”
Mr Justice Jackson said the man’s fluctuation was understandable.
“No other parent has ever been put in his position,” the judge said.
“It is no surprise that this application is the only one of its kind to have come before the courts in this country - and probably anywhere else.”
He added: “It is an example of the new questions that science poses to the law - perhaps most of all to family law.”
The judge said there had been a “tragic combination” of childhood illness and family conflict.
He said he had concluded that allowing the girl’s mother to make decisions about the disposal of her remains would be in her best welfare interests.
Lawyers representing the teenager, her parents, and hospital bosses had debated issues in the case with Mr Justice Jackson.
Barristers Frances Judd QC and Rob George had represented the teenager.
Barrister Stephen Crispin had represented the girl’s mother.
Barrister Helen Khan had represented her father.
Solicitor Christina Helden had represented hospital bosses responsible for the girl’s care.
Mr Justice Jackson had also sought the views of the Children and Family Court Advisory and Support Service (Cafcass) - which represents children embroiled in family court cases.
Cafcass had been represented by barrister William Tyler QC.