Help me with a Supposed-to-be-ex-step-mother?

Okay, so, this woman has been putting crap into both of our heads for 3 years. She's been telling me that I'm a fat looser who is going to get no where in life and that their whole marriage failing is my fault. Well, a lot of stuff happened (I got home from church one night, she started her crap, the cops got called because she called them, and then my dad did, but she was bluffing, apparently. She got arrested, and we had a restraining order put on her. ) and now she's spending the night every night, and I just don't know anymore. What's worse is that, I would forgive her, and I tried. She went to apologize to me, but it didn't feel right. It was like I could see it in her eyes. She was angry, not sincere. She was forceful with her hands, lifting my head up to look her in the eyes, and grabbing my shoulders. My dad doesn't get it. She always does what ever it takes to get back in, and then she's a nut again. She drinks, and her adult daughter said she was the same way with her when she was little. It's almost like, I've trusted her so many times, and all she's done is let me down. It doesn't help that she tried to apologize on Mother's Day. I saw my mom for twenty minutes today. I never really see her. She had to go when I was three. My step mom told me "I'm not your mother, I never was, and I don't want to be". So how am I supposed to feel on Mother's day? Please help me find a way to get my dad to realize. I've tried to talk to him, and so has the rest of my family, but he won't listen. He's getting sucked back in, and I'm afraid that by the time he realizes what he's done, it'll be too late. Please help me.