If she didn't have her license, legally this was probably the best thing to do. A hit-and-run is a misdemeanor in most states, and so is driving without a license. If she'd been caught driving without a license, she'd have her car impounded, she'd be brought to the station, have to call someone to get her, along with facing the fines. If she simply hits and runs, she gets mailed a slip for when to show up to court. I'm not saying what she did was morally right, but from a legal perspective you may as well drive away to avoid the trouble of losing your car.