Police said the woman was detained in the Londonderry area yesterday afternoon.
“She is currently assisting police with their inquiries,” a Police Service of Northern Ireland spokesman said.
Yesterday, a senior officer said they were treating the attack as attempted murder.
The 45-year-old victim suffered up to 35 per cent burns, including injuries to his face and neck, after being struck by a petrol bomb which was thrown through the living room window of his home at Ben Varden Avenue in the Waterside area of the city on Friday night.
He had to be pulled to safety by two neighbours who risked their own lives to enter the burning building.
The victim has undergone a series of operations at the Royal Victoria Hospital in Belfast where his condition was last night described was “serious but stable”. Two youths who used scarves to conceal their identity were seen running away from the scene.
PSNI Inspector Jon Burrows, area commander in Foyle, said the man was lucky to be alive.
“He was pulled from the property by two neighbours who risked their own lives. Contrast that with the actions of the two cowards who threw the petrol bomb. But, for the actions of those neighbours this man could possibly have died,” said Insp Burrows.