My fiancé (35M) and I (32F) threw a house party last weekend. My little sister (24F) brought her boyfriend (30M). My cousin (30F) and I were tipsily grilling him in a light-hearted way then I left to check on other guests. Later I come back and my sister’s boyfriend is flexing cartoonishly and saying he could take my cousin in a fight. Thinking it was a joke, I said “ha whatever she could totally take you” and walked off. When I came back again, they were actually arguing. He was calm, she was getting louder. I tried to diffuse it, saying we should work it out sober, and pulled my cousin away, but she kept yanking her arm back and even told me not to touch her. I got frustrated and told her she was escalating. She apologized, sulked away, and spent the rest of the night apologizing to me. I reassured her it was fine, and the party went on. Fast forward to a jog we did this today. She brings it up again, says she shouldn’t have apologized, that I didn’t have her back, and now she doesn’t know if she can “trust me to look out for her.” That stung because we’ve been best friends since childhood and I’ve always had her back. She even suggested my sisters boyfriend might be abusive (my sister literally laughed when I asked her about this). She told me I should apologize but I refused. It's clear he does genuinely feel hurt but I cant bring myself to apologize and frankly I think she has a lot of audacity to even ask. She was 3 hours late to the party, escalated a fight, and is now roping in other family members a month before my wedding. Of course they agree with her since she leaves out key details. She even denied I tried to pull her away until she finally admitted it just to say it didn’t matter. Nobody even remembers the fight clearly except her apparently. Now my wedding is in a month and she’s my maid of honor. I don’t want this drama right now, but I also don’t feel like I owe her an apology. If anything she owes me. AITA?