don't feel too bad, there was a 15 year old learning to drive 2 days ago and hit my fiance's mailbox and knocked the lid off.

If I were you, I'd just bring it up to her that she needs to pay atleast half of the damage. Your damager would cost around $250 (at a decent body shop). So if she could come up with $125, it'd be fair...seeing as how she's just 16 and probably doesn't have much money.