Last night A Hawke's Bay District Health Board spokeswoman said the woman was in a stable condition at Hawke's Bay Hospital.
The rural road just outside Hastings was closed for some time on Saturday while police investigated.
The owners of the property where the crash occurred were not home at the time. Yesterday the owner said it was not the sight they had expected to come home to, but said "I'm just pleased that the girl's all right".
The victim's family had been to their house since the crash, and saidwhile the 21-year-old had sustained some head injuries and broken bones, she was going to be ok.
The owner - who asked not to be named - said the crash had done some damage to their roadside fence, and fence leading into the property.
The 4WD had come to rest upside down against the property's wooden fence. It was removed over the weekend.
Other residents said they weren't sure how the crash could have happened given the layout of the area.
A nearby resident who had seen the crash scene said it appeared the woman had swerved off the road.
She said there were "very few" crashes around that area, as it was a "pretty straight piece of road".