The incident followed an argument between Maxine and her partner, she told 3News.
"He took off down the drive, went down the road, my sister was running after her.
"I'm feeling guilty because it was my birthday [party] and I should have looked after everyone.''
Oreen said Maxine had her spleen removed at hospital and suffered two punctured lungs, a broken leg and a fractured neck in the incident.
A Waikato Hospital spokeswoman said Maxine was still in a critical condition in intensive care this evening.
Police have asked anyone who heard raised voices or a disturbance in the area to come forward.
A witness reportedly heard shouting and said the girl had been walking away from an argument with the driver when she was run over.
Family and friends visited the crash scene yesterday.
Police have interviewed witnesses but still wanted to speak to anyone who was travelling on SH33 between 3am and 3.30am near the Whangamarino School.