You're being awefully nice. If it was my son he'd be totally responsible for it as that would help to ensure responsible driving. If it meant he takes the bus for the next 2 months, oh well. That would give him plenty of time to think about what he did as it could've been much worse. Was she on the cell phone by any chance since she apparently hit somebody from behind? At least she didn't hit a pedestrian. Good luck with the repair.