Sister is telling me what to wear to her wedding...and I’m a guest

Hey all,
im not entirely sure what to do about this situation. Both my sister and I are getting married over the next few months. My sister is in my bridal party, but she is only choosing to do a MOH only and I am not I’m her bridal party. Obviously for my party she has a bridesmaid dress to wear, but I wasn’t given a specific dress to wear for her wedding since I’m not a bridesmaid. A few days ago, my sister asked my fiancé and I what we were going to be wearing. I showed her the dress I bought and my fiancé said he’s wearing a “tan/ creamish suit”. My sister LOST it. She said my dress was “too dramatic” for her wedding and she said my fiancé cannot wear a light color suit because it will “take away” from her dress. Among my family and friends, I’m known as the “goth/edgy one”. I literally wear all black all the time. It’s my favorite color. Granted she is having a daytime summer wedding, but I’m just wearing a black, summer dress that I’m comfortable in. My mom even approved of it before I bought it. My fiancé, well don’t get my started on why him wearing a light colored suit will NOT take away from heron her wedding day. Anyway, things escalated and our attempts to comfort him or have a rational conversation were futile. My fiancé and I just decided to walk away and figured it was a “bridezilla” moment. My sister has a history of absolutely losing it over small things like that and after a day or two, she’ll clear her mind and apologize. Well it’s been a week since this happened and it had not gotten better. She maintains that we “absolutely cannot” wear our outfits and we “need to respect her wishes as family, not as guests”. She got our mom involved and my mom actually texted me and said “Jen is wearing what you’re asking her to wear for your wedding. If you’re going to make a big deal out of this, why bother even coming to the wedding ?” My mom then sent me pictures of dresses and suits my sister has “approved” us to wear.
This is clearly a messy situation. I’m totally willing to admit if I’m in the wrong, but her concerns seem a bit...irrational and controlling to me? And getting my mom involved to tell us to not come if we won’t get the outfits my sister wants us in? I dunno, something about things seems a little...bridezilla-y. Opinions, advice, anything 😱