With the amount of damage to that vehicle (and flat tire) there is no way she could have just driven home and not known there was a problem. Much less probably sparks flying up from the bike scraping the ground or at least the car not driving properly. My guess, out partying late or DUI, really neglectful. She's an idiot and should be charged. If she's not sure what she hit she should have stopped. It might have made the difference between life and death. Leaving the scene of an "accident with injuries".