Needing some serious advice

I found out my partner has been having an affair..for over a year...and I found out from that other girl she's with....a lot of lies came out..and things started to even make some sense...we were in a rocky place for a good while..but I never once stopped wanting to try and work things out...but I guess she really didn't..she wanted to leave me..said it many times..and had tried to leave...but I guess I always guilted her to stay....maybe I put myself here, made myself believe we could fix it..or maybe I was just being delusional within my own head.....but either way...finding out still kills me....

Right after finding out, about 2 hours later, she gets home...I was so angry, devastated, betrayed, heartbroken, lost, torn, and completely saddened....she ended up leaving again...but messages me saying she's going to hurt herself...because she's so hurt by realizing the pain she caused to two people she cared about...

So I ended up swallowing my own pain to comfort and support her...to be a friend because she had no one....and I love her so much. Of course I couldn't just do nothing...and on top of that too...if I didn't get to her when I did...I actually think something really bad would've happened...because it was actively in the process of happening...

I even swallowed my own pain and tried to help her get back with this other girl..since it seems shes wants her more then she wants me...and i just want her to be happy..

So now im in a position where im her best friend..which to me I guess is better then nothing at all, it hurts..but its still better, since she really is my person, the person I can go to for anything, the person the just gets me..

Now my problem is..shes talked about the other girl to me, how she treats her, and from a friend standpoint I can see just how dramatic and extremely toxic they're relationship is..shes told me when they fight, its really bad, where things are broken and it gets physical..to where the cops are called..

Im so scared for her, and ive told her this again and again, that this is bad...its toxic..and unhealthy..and a relationship is not supposed to be this hard..

Ive also expressed to her my feelings, she knows how much I love her, and care (obviously since shes technically still my wife)

I just really need some advice on what to do..I truly love this girl..and im genuinely worried about her and her well-being..im scared she going to end up one day in the hospital from this other girl ..