Natalie Crichlow died in Barbados after being doused in a flammable liquid and set alight while in bed.
Ms Crichlow, 44, of Colindale in London, was in Barbados to look after her disabled brother when she was attacked.
The mother of three had survived cancer twice and had two strokes in the past decade, according to her niece.
Ashley Best said her aunt suffered 75% burns to her body in the attack in Christchurch on 28 July. She died in hospital on 6 August.
Ms Best said: “The intruder broke in the house, then strangled her and then set her alight. She went into hospital and died of her injuries.
Ms Crichlow was born in Luton and she has three children aged 10, 20 and 26.
The family set up a crowd-funding page in an attempt to raise £8,000 to bring her body home.
Her niece said the family are concerned the Royal Barbados Police Force is not treating the death as a murder investigation.
A spokesman for the local police told the Press Association no arrests had been made.
A Foreign Office spokesman said: “Our staff are supporting the family of a British woman following her death in Barbados, and are in contact with the Barbados police force.”