AITAH I ruined my best friend’s wedding

I (25F) have been dating my best friend’s (25F) older brother (28M) for almost five years. He proposed to me a year ago. Me and my best friend have known each other since high school, and instantly clicked. She met a man about around two years ago and they quickly fell deeply in love, getting engaged a month ago.

Me, my bf, my best friend, and my best friend’s bf have all gotten very close and meet up one a week. At dinner three weeks ago, we decided to go bar hopping (we were having fun and it was a Friday night). I am a lightweight, so I tend to drink slowly and small amounts. During this night, I decided to let loose (I still drank in moderation but I drank more than usual).

My best friend started noticing I was getting drunk and so she suggested that we all go back to her house. Once we got to her house she told me to go upstairs and try to get to bed. The three of them stayed downstairs and continued to talk, drink, etc. When I came back down the stairs the next morning the two siblings were talking about me. I hid and eavesdropped and tried to hear things as best as I could.

My “friend” went on a rant about how I’m a liar who cheated on my fiancee. For context, I have never cheated on him and I genuinely loved him. She told him a whole made up story about everything I had apparently done behind his back, and he believed her.

Later in the car he told me that he wanted to breakup and when I asked why he said that he knew about my affair and he wouldn’t stand for it. I tried my best to convince him that I was telling the truth, but no matter what he never believed me. I acted like I didn’t know that my best friend was the person who lied about me and sabotaged my relationship. A year later I attended her wedding as her Maid of honor. This next moment would make up for the countless dinners, planning events, and the terrible bachelorette party.

When I arrived at the wedding, I went immediately to my best friend acting as if everything was normal little did she know I was gonna ruin her wedding. When the reception came about, I walked directly up to the groom and told him everything. The past year of manipulation and lies. After the shock wiped across his face, I went over to the officiant’s microphone and told everyone in the room about her crazy act. She walked down the aisle and everyone looked at her with disgust and disappointment. She ruined my wedding, so I ruined her’s.