I agree that it's not really her fault. Everyone has and continues to just be at her beck & call so of course.. she's going to continue the behavior. You get treated the way you let people treat you. so if your Dad is just jumping in the car every 2secs.. that's on him. HE is responsible to set his own boundaries. And if he doesn't see the issues with it, then that's something you or your Mother or whoever it's negatively effecting need to take up with him.

As far as your Mother and yourself, state your peace with her and then just move on. Mind you, I don't believe in cutting ALL ties with her esp. over something like this, as I feel you'll regret it after she's gone.

Kind of makes sense why her son stays away :P Sorry you're going through this though. Trust, I have some rather similar family members.. there's always one, right? lol