AITA for telling my best friend to leave my wedding after finding out she was secretly seeing my ex?

I (28F) have been best friends with Lily (27F) for over ten years. We’ve shared everything—breakups, heartaches, celebrations, and all the ups and downs that come with life. Lily was not just my best friend; she was my family. We were so close that when I got engaged to my fiancé, Tom (30M), I asked her to be my maid of honor without a second thought.

Tom and I had been together for almost five years, and while our relationship wasn’t perfect, we loved each other deeply. We were ready to take the next step, and I couldn’t wait to marry him. Our wedding was fast approaching, and I was busy with all the details, but everything was falling into place.

Or so I thought.

A week before the wedding, something happened that shattered everything. I came home one evening to find Lily in my living room, talking to Tom. They were laughing, and the conversation seemed casual at first, but there was an odd tension between them. I brushed it off, thinking maybe they were talking about wedding stuff or last-minute plans. But as I passed by, I caught a glimpse of something on Tom’s phone—a message from Lily that made my blood run cold.

The message was innocuous enough at first glance, but it was the last part that stuck with me: “Can’t wait to see you tonight… miss you so much.”

I froze. My heart started pounding. My mind raced, and I couldn’t stop thinking about how odd it was for Lily to be so comfortable with Tom, especially in a way I hadn’t seen before.

That night, after we had dinner, I confronted Lily about it. At first, she denied everything, but then I pushed her harder, asking if there was something going on between her and Tom. She hesitated, and then, with a tear in her eye, she confessed. She and Tom had been seeing each other behind my back for months. It started when Tom and I had a rough patch, and Lily had “comforted him.” But over time, it turned into something more.

I was livid. I couldn’t believe what I was hearing. I felt betrayed not only by Tom but by Lily, my best friend, the person I trusted the most. She apologized over and over, saying it was a mistake, but the damage was done. I was heartbroken and in shock. I needed some time to process what had just been revealed.

I was left with a tough decision. The wedding was a week away, and everything was set. I told Lily I couldn’t have her be my maid of honor anymore. She begged me to reconsider, but I felt like I couldn’t move forward with her in my life, let alone at my wedding. I also told her she couldn’t come to the wedding. I couldn’t stand the thought of her sitting there, smiling and pretending everything was okay while she had been hiding something so deep from me.

Lily was devastated, and she left in tears. But after she left, I felt this mix of anger and relief. I still love her like a sister, but I didn’t feel I could ever trust her again. The worst part? Tom was unapologetic. He was more concerned about the wedding being called off than the fact that he had betrayed me in the worst way possible.

I’ve since called off the wedding. I don’t think I can move forward with someone who’s willing to do this to me. Now, both Lily and Tom are mad at me, saying I’m overreacting and being too dramatic. They claim I should have forgiven them and moved past it, but I can’t seem to let go of what they’ve done.

So, AITA for calling off my wedding and asking my best friend to leave after finding out she was secretly seeing my ex?