Bethan Jones was flown to a special unit after suffering 50% burns
Bethan Jones, from Porth, Rhondda, had been three days into a round-the-world trip with boyfriend Alex Collins, 22, from Maesteg, near Bridgend.
Mr Collins was one of 81 people who died in the crash in Phuket. His body has now been flown home.
Miss Jones received 50% burns in the 16 September crash, in which the jet slid off a runway and burst into flames.
A total of 123 passengers, mostly foreign tourists, were on the One-Two-Go flight from Bangkok at the time. She was among the 42 survivors.
Two days later, she was flown from Phuket by military aircraft to a special unit in Bangkok General Hospital.
Her death is an immense loss to her family and also to members of our school and the wider community.
Steve Bowden, Miss Jones's former head teacher
Her parents Stephen and Jean, brother Dewi and uncle Terry had all flown out to be with her.
On Friday, the family issued a statement thanking family, friends and "the community of Porth and Rhondda and all Bethan's friends and work colleagues for their kindness and sympathy".
Miss Jones's death has been confirmed by the Foreign Office and the West London coroner, who said an inquest would be opened after her body has been repatriated.
The full inquests into the deaths of all the British victims of the crash will be held by the West Lincolnshire Coroner.
Tributes
Steve Bowden, head teacher of Porth County Community School where Miss Jones was a former pupil, said staff, students and ex-students were "deeply saddened" by news of her death.
He said: "Our deepest sympathy goes to her parents and family and she will be in our thoughts and prayers.
Alex Collins will be buried next week
Miss Jones was a "most able student" he said, whose main love was English and she had gone on to study at Cardiff University where she had gained first class honours, he said.
He added: "Bethan was a delightful, caring person who respected the views and feelings of those she came into contact with and was greatly respected by all who knew her.
"Her death is an immense loss to her family and also to members of our school and the wider community."
Mr Collins, who had also graduated from Cardiff University, had initially been declared missing following the crash but it was confirmed on Wednesday that his body had been flown home.
In a statement released by South Wales Police, his parents, Margaret and Richard, said: "Alex was a fantastic, loving son and our loss has left us with a hole in our hearts that can never be filled.
"He was an intelligent, polite and considerate young man with an extraordinary sense of humour.
"He had a great zest for life and both he and his girlfriend Bethan were really looking forward to this trip that he had meticulously planned for over a year."
His funeral is due to be held next Monday at Our Lady and St Patrick's Church in Maesteg, before he is buried in Maesteg Cemetery.
This One-Two-Go plane is similar to the one that crashed.
A Welsh woman has died in a Thai hospital from injuries sustained in the September 16 crash of One-Two-GO Airlines Flight 269 at Phuket International Airport, bringing the death toll to 90.

Bethan Jones, 22, from Porth, had been one of 42 original survivors in the crash, which her boyfriend, Alex Collins, 22, did not survive. They were three days into a round-the-world trip when the crash occurred.

Jones, whose family flew to Thailand in order to be with her, never regained consciousness after the crash, which left her in critical condition with burns across more than 50% of her body. Two days after the crash a military aircraft had flown her to a specialist unit at the Bangkok General Hospital for treatment.

Her family released a statement in which they thanked family, friends and "the community of Porth and Rhondda and all Bethan's friends and work colleagues for their kindness and sympathy".

Bethan's body will be flown home this weekend. Alex's body is already in Wales, and his funeral is scheduled for Monday.