When Gypsy-Rose Walker headed out for the night, her parents were comfortable that she was with a group of friends they liked and that they could follow her whereabouts on a family tracking app.

But at 2am, two of those friends were banging on Charlene and Grant Harkness’ door to tell them their daughter had been in a car accident and was being rushed to Christchurch Hospital.

Almost two weeks later, the 16-year-old is on life support and one of her teenage friends is dead. Her parents have been left caring for her 10-month-old daughter.

When the couple went back to look at the app, Life360, they claim it showed the car she was in travelling incredibly fast around a corner.

Family tracking apps are becoming increasingly popular for parents monitoring their children.

If the user allows, Life360 - reportedly used by more than 33 million parents in 140 countries - notifies parents if their children have driven above the speed limit, or been in a car crash.

Gypsy-Rose, 16, is on life support in Christchurch Hospital following a car crash that killed her teen friend. Photo / Supplied

Charlene Harkness spoke to the Herald at Christchurch Hospital where Gypsy-Rose is in the intensive care unit next door - suffering critical injuries.

She’s suffering brain swelling on both sides of her head.

“Brain injuries can go north or south very quickly,” said Harkness.

“The nurses were saying it’s like the big man upstairs wrapped her in bubble wrap from the neck down, there’s not a toenail out of place. But we’re in limbo now, trying to find out what happened.”

On July 30, Gypsy-Rose, who had been studying at a parents’ college before the crash, told her mother she was headed out with friends. A group of them gathered to drive around town in the early hours.

Gypsy-Rose was the front-seat passenger in a car driven by a 17-year-old friend.

Harkness was told by the youths who alerted her that the car her daughter was in had travelled with another car to pick a person up from their house.

When those in the second car realised Gypsy-Rose’s vehicle hadn’t made it, they circled back to find the car on the side of Greywacke Rd in Harewood, having hit a power pole.

In the car with Gypsy-Rose were the driver, who was killed, and a woman in the back seat who was hospitalised with critical injuries. A teenage boy who was next to her walked away relatively unscathed.

“She was an unidentified female at the time. They knew they had a dead girl and one really broken, another with a brain injury, but they didn’t know who they were,” said Harkness.

“When Grant arrived, she was already in theatre and had brain surgery for hours.”

Police have told the Weekend Herald it’s too early in the investigation to provide details of the crash.

The Herald has approached the driver’s family for comment.

Gypsy-Rose, 16, is on life support in Christchurch Hospital after a car crash that killed her teenage friend.

According to Harkness, her daughter had been spending time with a group of teens who would often go out for drives late at night as a way of entertaining themselves.

“I hated Gypsy going,” said Harkness.

“We’re not angry at [the driver] or the family, I’ve got a daughter who’s made mistakes, but these kids think they’re invincible and they’re not.”

She’d noticed that her daughter’s friends weren’t drawing from any support when it came to mental health or ways to process the stresses they experienced.

“I don’t worry about my girl being with these kids,” the mother said.

“But I worry about what they get up to, I don’t like the fact they get into fast cars at this time of night - they choose the wrong time and places to entertain themselves.”

As of this week, Gypsy-Rose has shown small signs of improvement.

“We brought her baby in and she kept trying to grab at the wires, but then she touched her arm and all of [Gypsy-Rose’s] vitals suddenly calmed,” she said.

“We’ve got people all over the world praying.”

The incident comes after a string of fatal crashes in the Canterbury region.

Over the weekend, a car carrying a family bound for Mt Hutt crashed and killed two children, critically injuring a third. On Tuesday, a legal executive was killed after her car collided with a teenager’s.

In the week that Harkness has spent in the intensive care unit, she’s seen seven other people admitted into the ward for crash-related injuries of a serious nature.

An app told Gypsy-Rose’s mother the car was travelling at 147km/h around the corner. Photo / George Heard

“The Twizel girl is here,” she said, referring to Olivia Oughton, who crashed into a house on Mackenzie Drive two days before the Harewood crash.

“These kids are going out in the middle of nowhere, which is dangerous enough, they don’t know well enough how to drive or the conditions they’re driving in, and now they’re dying.”

It’s a story all-too-familiar for Senior Sergeant Mike Jones of Christchurch road policing.

Jones told the Herald his message to teens was the same as to anybody behind the wheel - “drive to the conditions”.

He mentioned that for every kilometre slower a person drove, the driver’s chance of a fatal crash is reduced by 6 per cent. In general, he said, speed has a huge impact on the outcome of a crash.

“It’s a factor in almost a third of all fatal crashes,” he said.

“Speed is the single biggest determinant in whether anyone is killed, injured, or walks away unharmed. We all have a role to play in keeping the roads safe.”