Teen critical after botched Qld carjacking

A teenager is fighting for her life in a Gold Coast hospital, while another is in police custody after an apparent botched carjacking.

The 15-year-old girl suffered severe head injuries when she was flung from a car on a suburban street in Helensvale just after 7.30pm on Thursday.

The girl had allegedly been leaning through an open door brandishing a knife and demanding a 24-year-old woman give up her car.

The panicked driver drove away at speed, with the girl's head hitting either the pavement or a parked car when she was thrown clear of the vehicle.

Unaware the girl had been injured, the woman called police after driving a short distance to report the attempted robbery.

A boy who was with the girl fled the scene. He was arrested on Friday and is in police custody.

"She just believed that she'd managed to speed off," Detective Senior Sergeant Mark Procter said of the driver.

"She seized on an opportunity at the time when she thought they'd pulled their hands out of the car."

The girl was placed in an induced coma and remains in critical condition at the Gold Coast University Hospital.

Det Snr Sgt Procter said the incident began when the teens approached the woman at Harbour Town Shopping Centre and claimed they were being followed by a man.

She offered to give them a lift and they asked her to drive them to Mullewa Crescent, eight kilometres away.

Mr Procter said police were confident the story given by the pair to gain the lift was a ruse and the driver, who suffered a small cut to her hand, was deeply affected by the incident.

"She's done what most of us would do," he said.

"She was pretty shaken up."

Local resident Angus Knox said he could see puddles of blood on the road outside his family home when he arrived at the scene.

Mr Knox, who was initially suspected by police to be the missing boy, had been concerned something had happened to his grandmother inside their home.

"I'm pretty sure there was some blood on the road. You could see big puddles of it. It wasn't cool," he said.