Samantha Broadhead and Jack Ault have been charged with attempted murder and arson after the fire in Clearwater, about 20 miles west of Tampa on Florida's Gulf Coast.
Clearwater Police Department detectives say the young couple poured gasoline on Nancy Broadhead's bedroom floor and bed, and then set the room aflame. Police say the pair escaped in the mother's 2007 Ford Focus.
It was unclear if either suspect had an attorney. There was no answer at a listing for an Ault in Clearwater.
The girl's mother was awakened by a smoke alarm and managed to escape. Authorities say Nancy Broadhead, 47, sustained serious burns and smoke inhalation. Her injuries were not considered life threatening.
Samantha Broadhead later returned to the scene and agreed to go to police headquarters for questioning. Jack Ault was located at a friend's house and taken into custody.
Police spokeswoman Elizabeth Watts said a motive was "probably just typical teenage angst."
Watts said there was ongoing tension between Nancy and Samantha Broadhead, which escalated Monday when the mother confronted her daughter about stealing some of her cigarettes.
Ault has been taken to a juvenile facility, and Samantha Broadhead is undergoing a mental evaluation.