Bitchy “friend” sharing relationship problems - what should i do

So im not going to lie, my boyfriend and I have had problems with our relationship that I haven’t fully recovered from. I caught him speaking to this girl on social media inappropriately, and I ended things. We were engaged and have two kids together. I ran into a mutual friend of ours (originally his friend that i met through him) shortly after and she asked about us. I just made a face and she asked what was wrong so I said that things weren’t doing so well as I caught him speaking to this other girl but I wasn’t sure how things were going to play out. I told her this as I had become pretty close to her in the three years since I met her. Also when I found out her boyfriend had actually physically cheated on her I let her know. I told her that I wasn’t doing it to cause drama but if it were me I would want to know and be able to decide what to do for myself. She thanked me, and ended up staying with him and since then neither of us have brought it up.

So I felt like she would be a bit understanding. Anyway flash forward to now. I forgave him which I know not many would do, but he proved it was just talking, we went to couples therapy, and now he agrees to be more open and honest about his social media which he has. He’s honestly a different person. But that girl he was talking to is now with one of his best friends. No one knows, or knew, except my boyfriend, our friend i told, and me. (And her of course)

Obviously I felt uncomfortable about him going around her so when he was invited to his best friends (her now boyfriend) birthday party I told him I wasn’t comfortable with that yet. I guess the girl I told (our friend) suspected why we didnt attend and she ended up telling everyone at the party I was being an insecure bitch for not “allowing” him to go. She said my boyfriend cheated on me with that girl, that we needed to decide whether we were going to be together or not, and stop being on again off again.

I was pissed. It’s not like we made this public, I was trying not to make things weird by going, she was cheated on as well actually physically cheated on and i never said a word. And she’s still with the guy too. I also know for a fact her boyfriend had to quit his job because she didn’t want him around his coworker (who he cheated with.) So for her to say that was hypocritical. Im so mad. Part of me wants to be the bigger person but the other part of me wants to expose her. She acts as if her and her man are so perfect and Im not one to judge for staying with a “cheater” but to say all this about my relationship when she’s just as bad is so rude. It’s not her business to share. And yes I know I told her, but I truly thought as someone that was cheated on she would get it. I still dont think she had any right to say all that. What would you do?