I don't want to get in an ill-begotten car with my college girlfriend
Is she an erratic driver?
Yeah, she drives very dangerously. Plus I'm pretty sure the car is stolen.
Your gf shouldn't steal cars. You shouldn't be involved with someone like that or drive in that car.
I know, but I'm scared of her. She has a really bad temper and I don't know what she might do if I refuse.
It doesn't matter if she is your girlfriend or not, getting into a stolen car is wrong and you might be responsible for it too. Perhaps it's best to call the police, because it sounds like you might be abused. Your health matters and you deserve better relationships!