Would I be wrong to stop talking to her?

My baby’s dad would always snatch his phone away from me. Hide his phone or sleep with it in his hand or something. He made a statement that if he ever cheated on me I would never find out because he’s too slick. I found out he was talking to his “friends” ex while his “friend” was in jail. She was sending pics of her ass and whatever else I don’t know. He’s on Facebook liking all these women’s pictures and even messaging them “hey beautiful” stuff like that. I was telling his mother that he’s abusive to me physically, mentally, emotionally, and financially. None of her business but since she wants to act like he’s the victim I had to let her know. He tries to make me seem like I was wrong for wanting to leave. As I told his mom about him possibly cheating on me she says “I knew he was talking to someone a couple months ago and I told him it was wrong” blah blah blah. Didn’t even listen after that because I was pissed. How could she be a woman and sit here and say nothing? She had an abusive past as well so I just don’t get how she can beg me to stay with him. I feel like I literally hate them. Like I know it’s not her place but wow. I don’t know maybe I don’t get it. Maybe this is what I deserve. She looks me in my face saying she loves me and this is what I get?