AITA for not wanting to attend my best friend's wedding after she slept with my ex?

So, my (25F) best friend (26F) and I have been close for years. We went to college together, shared everything, and supported each other through breakups, family issues, and everything in between. We’ve been through thick and thin, and I’ve always trusted her completely.

About a year ago, I broke up with my boyfriend, Jake (28M), after three years together. It wasn’t an easy decision, but we were constantly fighting, and I knew deep down it wasn’t the right relationship anymore. We agreed to part on good terms, and I haven’t really thought much about him since then.

Fast forward to a few months ago, my best friend got engaged to her long-term boyfriend, and the wedding was scheduled for this coming summer. I was so happy for her, and of course, I was excited to be the maid of honor. Everything seemed perfect… until I found out that she slept with Jake, my ex.

I found out about it when I was at her place one evening, and I noticed a text conversation between her and Jake on her phone. I was shocked, but I didn’t confront her right away. The more I thought about it, the angrier I got. I couldn’t believe she would betray me like that. She knew how much he hurt me, and yet she went behind my back and slept with him after everything I went through.

When I confronted her about it, she apologized, saying it was a one-time thing and that it meant nothing. She said she was just “caught up in the moment” and that it was a mistake. But what really upset me was when she said, “I never meant to hurt you, but it just happened.”

I’ve tried to move past it, but I just can’t shake the feeling of betrayal. She’s asking me to be at her wedding, but I’m really struggling with the idea of standing by her side as the maid of honor after what she did. Part of me wants to be happy for her, but the other part of me feels like she completely crossed a line.

Now, I’m torn. I know weddings are important, but I don’t know if I can move forward and be in her wedding when I feel so hurt and betrayed. I haven’t made any decisions yet, but I feel like I can’t fake my excitement when all I feel is resentment.

So, AITA for not wanting to attend my best friend’s wedding after she slept with my ex?