I'm so sorry your dad isn't being much help to you, like I said i've been through this (going to my mum and expecting support but getting none) so I know how upsetting it is. Does he know about her trying to crash the car? That should be something he should address really, I mean if she tries to do it again she could at worst kill or seriously injure you, herself, anyone else in the car and other motorists. Then it becomes more than just about you and her, it's about other people using the road and their safety. Is she getting therapy of any kind?
Oh and for what it's worth, a more direct answer to your question, your health is #1 priority. If she's trying to injure you, you need to stay the hell away from there.