Helpppp

I need some outside advice. I have a 2 year old daughter and her father and I have not been together since I was 3months pregnant. Now we both used to share her 50/50 and he started dating a underage girl, who would make comments like "I am her mother" and other things along the line of that. I have spoken both to her father and he girlfriend that it is very disrespectful as to if I try to date my ex tries to fight the other boy and has made comments such as he would murder someone. Her father and I have gone to court and I got 75% custody (he gets her one week out of the month) today my daughter comes home and my daughter tell me this other girl is taking showers with my daughter. To me it's rude and disrespectful and confusion for my daughter as she grows. Any outside opinions or thoughts on what I should do appreciated!!