Baby Momma Drama

So my Fiancée who I have a child with (2 months old) has a really difficult relationship with the mother of his child. For more context they were never together before nor after, She fell pregnant of course but during her pregnancy she said and did a lot of hurtful things to him (out of anger for him not wanting to be with her) and effected their relationship with eachother and coparenting. She makes his life a living hell and it affects him a lot and I’m scared it’s going to affect our relationship too. I know his circumstance and im very understanding but she extreme disrespectful to him and me. She calls me a bitch and every time he wants to be with his daughter she says go be with your bitch and since having our baby she says go be with your other family. She stresses him out, me out, and even his mother out. She doesn’t work and lives comfortably with her family and the money he gives her weekly. She isn’t looking for work and threatens child support on him regularly when he says something she doesn’t like. She also will not let him see her and he can’t even take his daughter out unless he takes the both of them out. She also only lets him see her at night which makes me very uncomfortable but how else is he going to see her. One time I called him when he was there bc I needed help with something and she was listening through the door and threw all of his stuff out and didn’t let him say bye to his daughter. I try to give her the benefit of the doubt knowing she’s hurt but I’m getting sick and tired of it. I don’t know what I can do in this difficult situation but be there for him but I’m getting sick and tired of her disrespecting me and our family. She definitely has mental health issues but she really is a tyrant and thinks that she should be treated as his girlfriend and almost makes me feel like I’m the other woman. She even called his mother a traitor when I want out with her like girl what?!? He doesn’t deserve it and neither does their daughter. Neither one of them wants to involve the court (even though she threatens him) but it’s getting to a point that he needs to do something about it. Ladies idk what to do😭😭😭 Should I put my foot down and tell him to put her in her place?(he already tried multiple times she just gets more difficult /disrespectful) Should I let it play out and see if she grows up? I need help yall she’s driving me crazy I don’t even want to get married anytime soon with her acting like this I just wish we could have a peaceful relationship and they can peacefully coparent 😥