AITA for telling my sister I hope her husband cheats on her after she ruined my wedding dress?

So, here’s the deal. I (29F) have been engaged for about a year, and I’m getting married in three months. Like many brides, my wedding dress is a big deal to me. I spent months picking it out, and it cost more than I care to admit. It’s a gorgeous custom-made gown that I was keeping at my mom’s house because I wanted to avoid any “accidents” at home (I have a dog that sheds like crazy).

My sister (34F) recently had some sort of “life-changing epiphany” and decided she’s done with fast fashion and wants to live a more “eco-conscious” lifestyle. Cool, right? Except she’s taken it to a weird level, constantly shaming me and others about our choices, like buying new clothes instead of thrifted. She’s also become super into DIY projects—most of which end up looking like a Pinterest fail, but whatever, I wasn’t going to say anything.

Fast forward to last weekend, I stopped by my mom’s house to check on the dress and make sure everything was fine. When I opened the garment bag, my heart legit stopped. My sister, in all her DIY glory, had dyed my wedding dress. Apparently, she thought the white was too “traditional and boring” and decided to “upcycle” it by dip-dyeing the bottom half in this hideous tie-dye rainbow pattern. HER WORDS: “I made it more fun and unique! You’ll stand out!”

I. LOST. IT.

I screamed at her, and she just stood there, acting like I was being overdramatic. She kept saying she was “just trying to help” and that “it’s just a dress.” I told her she’s a selfish psycho and to never speak to me again. Then, and this is where I might be the asshole, I said, “I hope your husband gets so sick of your controlling, self-righteous BS that he cheats on you.”

She started crying and called me a bunch of names, saying I crossed the line. Now my mom is mad at me, saying my sister was “only trying to do something nice” and that I didn’t need to take it “that far.” She’s insisting I apologize for the cheating comment, but I feel like I was justified in saying it. My fiancé thinks my sister is nuts, but even he raised an eyebrow at that last comment and said I might have gone too far.

AITA for saying what I said, or is my sister just the worst?