I think I have it figured out now why his girlfriend is still sticking around. He has guilted her into thinking she owes him money for ruining his piece of [Bleeeeep!] truck that was probably on its last leg when he let her drive it, so now it's all her fault. The poor girl now thinks she is indebted to this miserable family for $11,000 and is going to school so she can get a good job to pay off her debt.
You have already showed your lack of respect for her in the past, just let her go.