Friendship help

I have a friend that I’ve known for a couple years that has made some bad choices lately and has really hurt my feelings. Backstory:

She “Jen” married my husband’s best friend, “Jake” a few years ago. It was a volatile relationship from the beginning and they fought all the time.

Jake has been over to our house a lot in the past 2 years and would often vent about their problems. He is a good guy and a good friend to us. Never been angry or violent with us. He made accusations that she would get blackout drunk and hurt him, yell at him, and take his Adderall pills. He also said she has bipolar disorder. I’ve never asked her about that. I’ve since kept that all to myself. I tried to be a good friend to her. She had mostly been a good friend to me. She had her own circle or friends before she met him. Jake, my husband, and their other friends and their wives have all been very close for many years, some since high school. We’re now all in our thirties. The only reason she knows any of these people is because of my husband.

A few months ago, Jen called the police on Jake and claimed he hit her and kept her from leaving the house. She kicked him out, she pressed charges, he pled not guilty, and they went to trial. He was found guilty of one misdemeanor charge. They are now divorced.

Before the trial, Jen reached out to me and some friends for support. She told us she had to “get ahead of the situation” before Jake could deny anything. These are friends my husband and I have been close with for many years, one since 5th grade. Before the trial, Jen wasn’t very close with this group. Then she started eliciting sympathy from us, saying how awful Jake treated her, how all she did was give him everything, etc. She would often ask me for information about Jake since she knew he and my husband would talk. I didn’t comply with her requests as it put me in an uncomfortable situation. Their messy divorce ultimately put a strain on my marriage because we were forced to take sides.

I recently found out that for the past few months, Jen has secretly been dating one of Jake’s oldest and closest friends, “Aaron” unbeknownst to him. I have also known this person for many years. They bonded over talking about how awful Jake is. He is now living with her. Jake thinks he and Aaron are still friends and has no idea they are together.

I told her I was upset and couldn’t believe she would hide something like this for several months. She trusted me with her divorce stuff, but not this? I even asked her if she was on because it didn’t seem like something she’d do. She said Aaron told her to lie to her friends so Jake wouldn’t find out. She was with him the whole time she was eliciting sympathy from me about Jake. Now she’s begging to talk to me to explain her story.

Our mutual friends want me to hear her out. They don’t get why I’m so upset. I’m angry and want to forget about her completely, but she has become close to my friends now since the trial. I don’t understand why she’d want their friendship when she already has so many other close friends. It feels very manipulative and two-faced. If Jake is truly so awful, why date his close friend? And be friends with his friends? I would personally want nothing to do with my abuser or any of his friends. None of this makes any sense to me.

What should I do?