Good for you, guest. It burns me up that people put up with shit from their family members that they would not put up with if that crap were coming from a stranger or even a friend. Just because she is your mom doesn't give her any right to emotionally blackmail and abuse you. And you don't have to take it.
Where the hell was she, when you went through breast cancer, for chrissakes? We all know: worshipping your sister's Almighty Baybees.