Trying to understand

I stayed in an abusive relationship for years. I finally got out.

I’ve been free for a couple months. I noticed that he had moved on. With a girl he’d met last year while I was dating him. She’s 21, recently divorced, and has a kid. My ex was still sliding into my DMs. I reached out to tell her hey I’m not responding but your boyfriend is telling me he wants to be with me. Turns out he was sleeping with both of us for probably 10 months. He called both of us his girlfriend.

She said she was glad to have this information to move on. The next day she posted photos of them together to her profile. I asked why she’s staying. She doesn’t consider this cheating. She says because she knew of me it’s not. I’m just trying to understand. I told her about the abuse and she said what I suffered wasn’t as bad as her ex husband. I told her he does drugs and used to deal. Doesn’t phase her. She says she’s been cheated on and this won’t be the last time probably (how sad is that to say. Find a good man, girl!). She won’t leave because she doesn’t know both sides of the story like he’s going to be a reliable narrator. I sent her piles of proof. Also because she has no friends and his close with his friends (surprise they’re alcoholics with toxic traits). She’s scared she’ll get her kid taken away (that’s not on me???). You’re letting a guy who cheated on you, abused his exes (not just me), and is tied up with drugs around your toddler. I’m not the reason your kid will be taken away. I don’t know how you get all this proof and just say I’m going to keep building a relationship with him. Like what?????? Meanwhile he’s telling me he loves me but then threatening my life if I do anything rash. I’m not doing anything. I followed girl code and tried to help her out. But maybe they deserve each other if they’re both cool with cheating.

Edit: I want him to be happy. Just because he would beat the shit out of me doesn’t mean I don’t care about him as a human. I want her to be safe because she’s young and naive. Talking to her you can tell. I bring up her kid because I wouldn’t just want a father figure I’d want a good father figure for my kid. I miscarried my exes and i’s kid because of him. A tiny part of me was relieved because I didn’t want a kid to grow up seeing me beat or get beat themselves. I actually talked him up as a good guy to her but with heavy triggers. I’m just trying to understand how she took nothing to heart and belittled what I went through because it “wasn’t as bad”