My father is very verbally abusive and I haven't spoken to him in two years for this reason. Since my husband and I unfortunately live with my parents, he automatically assumed he would be taking care of my child and buying it everything it needs because "we're unfit parents." I've told my mum that he's not allowed anywhere near my child and we plan to move out before our baby is born. If I were telling him, I'd tell him exactly what I think, so I think you should do the same. Be calm and explain why you won't let her near your kids. Good luck!
It sounds like a tough question. If you aren't living with her now, It should be easier that if you are. You will probably want to set clear boundaries with her while being as respectful as possible at the same time. I would suggest being gentle in how you approach the topic so that you can maintain a relationship so be careful with accusatory statements and how you phrase things. Try to phrase things as positively as possible and try not to throw around blame. It seems like You want the best for your baby so really think it out before you talk to her. You can always consider family counseling as a way to tell her so there is an neutral person helping keep things calm.
Everything u just said i would tell her the exact same way. I think your a bad influence on kids and i dont want my children around that. So until you can get your act together the baby will not see you.