Bipolar mother

Hey guys I need your thoughts on this. I dont want my mother to really be involved in my child's life due to the fact she is bipolar schizophrenic. Back story when I was younger I watched her cheat on my dad for years I seen her steal thousands of dollars from my grandmother she started taking my money. She was abusive and I basically had to raise myself my dad worked two jobs so he wasn't home alot. Now that I'm trying to have a child she has become obsessive. We got into it a few days ago because she told me I wasn't going to keep HER CHILD away from her. Do you think I am right in keeping my child away from her?