Have you ever dealt with a crazy baby mother ?

Im with a guy who has a child.. I love him & her!!! But the baby mother wants me no where near her kid.. I try and help brush her hair when I'm there and feed her. I'm not trying to takeover her role as a mom but as a girlfriend who cares... I cannot see a child suffer while I'm around. I think being in a relationship with a man who has kids is totally fine. Maybe he needs your motivation. I'll never put a man down, unless he has disrespected me. Sometimes I feel woman tend to get jealous of the baby father's new girlfriend but some get along .. have you ever had a crazy baby momma in your life? Did it ruin your relationship? What do I do, I love this little girl and her father but I cannot continue with the bm threats anymore !!