Samantha Robertson is in an induced coma in Auckland's Starship Hospital after the terrible incident in Morrison Rd, Pukekawa, northern Waikato.
It is the latest in a series of cyclist accidents. Last month Auckland man John Tangiia, 37, died after he was dragged under a truck in Parnell.
Samantha's father, John Robertson, who flew from Christchurch to be with his daughter, said she had been swimming in a friend's pool when she had hopped on her bike to ride home.
That was why she wasn't wearing a helmet or high-visibility vest as she usually did, he said.
Robertson struggled to put into words the shock he and Samantha's family were feeling as they sat helpless by her bed.
"You've got no idea, mate," he said. "But she's a free and strong spirit who will probably pull through this, she's that strong.
"That's what we're hoping for. She's fit and she's active and she's healthy and she's young so she's got all of that on her side."
He said the nursing staff were happy with the progress she was making. Robertson and Samantha's mother Sherry Coulson were meeting doctors last night for the latest prognosis.
A family friend, who did not want to be identified, said Samantha was a "strong wee girl".
"We're all hoping she's got the strength to pull through."
She had spoken to the girl's mother yesterday, who also remained positive.
"They put her in an induced coma and basically they're just waiting for a couple of days to hear her progress. So basically it's just a matter of waiting at the moment."
Police said Samantha had overshot the end of a driveway and ploughed into the path of a car on the 100km/h road.
Sergeant Wayne Paxton came across the crash as he drove home.
"It was pretty chaotic. She was still on the road, it had obviously only just happened. She was in a pretty bad way," he told the Herald this week.
He had bandaged the worst of the girl's injuries, while her mother sat beside her constantly talking to her and urging her to be brave. "She was distraught, but she did a really good job. The injuries she was looking at no mother or father wants to see."
Samantha is a student at Pukekawa School. The board of trustees chairman Chris Ahearn said the school and local community were in shock.
"It's certainly close to the bone because it's a small community and people know each other so it's certainly a sad state of affairs and we just wish her well and want her to get better soon."
A spate of cycling deaths in recent years has sparked calls for more investment in cycle safety. Eight cyclists died in New Zealand in road crashes in 2012 and last year.
- Herald on Sunday/additional reporting John Weekes
