My mom hates my dad, and according to her I'm: "just like him"?

Sorry this is going to be a long description... I love my dad, even though I know he's done a lot of things to hurt my mom, sister, and myself, but he's my dad. I don't see him often, and he still does things to hurt my mom sometimes, but I still love him. I live with my mom, since I'm 19 and going to college still, and almost every day we get into arguments over stupid things, I don't know what to do. One minute we're just discussing something calmly, and the next she's accusing me of calling her stupid, and that I'm: "just like my father" and that I should move out, or leave. I know what she means by that phrase, and I have asked her why she says that I'm "just like my dad," but she is quick to deny vehemently, that she ever said that, and then says how good a son I am, and how bad a mom she is. At this point, I feel bad about bringing it up, and try to console her. I say that because this has happened many times. She can be very irrational, she's always anxious, and has been mistaken as a hypochondriac by many people, she's quick to forget, and her mood as well as tone of voice can change in a flash. I can't stay mad at her, but it hurts to be compared to what she hates most in the world, what's worst is that it's my dad... if anyone is out there, please.... I need advice....