AITA for not forgiving my sister for sleeping with my husband?

This past summer I (28) found my sister (30f) and (soon to be ex) husband (30) in bed together. I got home late and the two of them were fast asleep in bed together, naked. I lost it and they were falling over themselves apologizing and saying it was the biggest mistake. I made the two of them leave and then I told my ex I was filing for divorce the next morning, something I followed through on.

They both begged me to change my mind. I ignored them and continued on. My ex eventually realized I was truly done when I wouldn’t even consider marriage therapy with him and when I gave him back both rings which were rings from his family. I wanted to have him gone after finding him with my sister and had no interest in selling them or anything for money. I just wanted him gone and to send the message that I was not going to work on our marriage.

After leaving my house my sister went to our parents and my dad came to stay with me leaving mom with my sister. He was there and his support meant everything to me. And in all of this he has been the most supportive. Mom has offered some support, but she also wants me to forgive my sister. She brings up how much my sister has apologized.

Of course she and my ex didn’t use protection and she got pregnant. This was a big deal and my mom made this a very big deal to me. My sister’s marriage ended last year because she had many fertility problems (PCOS, endometriosis and her eggs weren’t healthy enough to try IVF) and her ex-husband wanted biological kids. It was a big blow to learn her chance for bio kids was so low and then her marriage is over. I was there for her throughout and said I would help her however I could. I even said I would be open to carrying a baby for her in the future. I loved my sister. We were so close. So her actions hurt more than even my ex’s. And then she was pregnant. She had an abortion. She told me she knew I would never be able to accept her if she had his child and she wanted me more. She told me she would not do that to me. My mom begged me to stop her aborting and forgive her when she was willing to go that far for me. My dad had to stand in and help me because mom was so mad that I was letting her go through with it. She broke after the abortion and her messages got more pleading. But I wasn’t willing to forgive her.

And I’m still not. I won’t forgive her, I made that clear. I also won’t talk to her. They claimed it was just that one time because they’d been drinking but I can’t ever feel the same about her. I helped her through the worst time in her life, offered to help her have kids one day in the future and she does that to me. I want her to suffer for what she did. I don’t want to let her off easy. I don’t want to act like things are okay or give her another chance. I don’t want to be stabbed in the back again.

Dad was with me for Thanksgiving and Christmas because mom insisted my sister was going to be there. I refused to be there for that reason. My mom is on my case bad about it. She told me I’m behaving worse than my sister. That my sister made one mistake in a moment of alcohol infused madness but I’m making sure my sister hurts and driving the family apart. She told me we were always so close and I confirmed we had been and I told her she shattered all that. I told her I regretted being a good sister to her because it got me betrayal from the two people I loved most in the world and I’ll never be able to stop associating her with doing that to me.

AITA?