ANGELA Pershouse says she was feeling "pissed off" when she threw her cigarette into grass at Toolooa causing a fire.
The fire quickly spread through a paddock off Dalrymple Drive.
Police prosecutor Gavin Reece said Pershouse had been walking down Dalrymple Drive at 6pm when she stopped at a vacant lot and deliberately lit the fire.
"It engulfed approximately half an acre," he said.
Fire officers were called to put out the grass fire.
Mr Reece said that when police officers questioned her nearby Pershouse at first denied lighting the fire but then went on to say she was sorry for lighting the fire.
"She says she deliberately lit the fire with a cigarette as she was pissed off," Mr Reece said.
Pershouse, 24, pleaded guilty in Gladstone Magistrates Court to lighting an unauthorised fire with no permit on September 12 last year.
Defence lawyer Jun Pepito said Pershouse suffers an intellectual impairment and instructs him that she is on medication.
He said she accepts being responsible for the fire and had been smoking when she threw down a lighted cigarette.
Magistrate Penelope Hay said the fire was serious as officers had to attend and extinguish it.
Ms Hay said she would not sentence Pershouse over the fire offence until the court had more information about her condition.
The sentence was adjourned until Friday.