AITA for telling my friend I couldn’t attend her wedding after finding out she was dating my ex?

I (30F) have been friends with Sophie (29F) for over a decade. We met in college and hit it off instantly. Over the years, we became very close, sharing everything—our dreams, our fears, and our personal lives. She was always someone I could trust completely. I thought nothing could come between our friendship.

I had a long-term relationship with Ethan (31M), and we were very serious about each other. We dated for about 4 years, but things started to fall apart during the last six months. There was a lack of communication, and I started noticing things that made me question if we were really on the same page. We broke up amicably, and I thought I’d be okay. We didn’t have any bad blood between us, and I genuinely thought we’d both move on.

Fast forward a few months, and Sophie announced she was engaged to a guy. I was excited for her, of course. She told me she had met someone amazing, and I could tell she was head over heels. I immediately congratulated her and offered to help with wedding planning. I was happy for her, or at least I thought I was.

The weird thing, though, was that Sophie’s fiancé seemed oddly familiar. I’d never met him, but something about him nagged at me. I couldn’t put my finger on it. Then one night, at a party Sophie hosted, everything clicked. Her fiancé was Ethan. The same Ethan who had been my boyfriend for 4 years. I froze when I saw him, and I couldn’t even process what was happening.

I tried to approach Sophie after the party, and she told me how happy she was with Ethan. She said they’d been talking for a while, and things had progressed pretty quickly between them. At that moment, I felt my stomach drop. I tried to be happy for her, but it felt like a betrayal. I didn’t know if I could accept this.

When I confronted her about it, I told her that I felt uncomfortable with her marrying my ex, especially since we had just broken up a few months ago. She said that they had been friends before they started dating, and it was a natural progression. But honestly, I felt blindsided. She had never mentioned anything about being interested in Ethan, and it was hard for me to accept that she’d gone from my best friend to dating the person I once loved.

I tried to keep my emotions in check, but I couldn’t. I told her I wasn’t comfortable attending the wedding anymore. I felt like she had crossed a line by dating someone I had been so deeply connected to, especially so soon after our breakup. She was devastated, and so was I. She cried and begged me to reconsider, saying she had no idea I would feel this way. But I felt like she should have known. She had always been someone who knew all the intimate details of my past relationships.

I’m feeling conflicted because I love Sophie, and I want her to be happy. But I also feel hurt and betrayed by her actions. It feels like a huge violation of trust and respect. Now, she’s not talking to me, and I feel like I’ve lost my best friend. Our mutual friends are also divided. Some think I should just let it go and attend the wedding, while others agree that I have every right to be upset.

So, AITA for refusing to attend my best friend’s wedding after finding out she’s dating my ex?