Bride bans fiancé's sister from bridal party after dress fitting. AITA?

"AITA for telling my fiancé I don’t want his sister to be a bridesmaid after she ruined my dress fitting?"

My fiancé (29M) and I (28F) are getting married in March. His sister (25F) and I have never gotten along. She has a habit of “joking” about me being uptight and says I’m stealing her brother away.

Last week at my dress fitting, she tagged along with my MIL. I was already stressed, but during the fitting she made multiple comments about how the dress “wasn’t very flattering” and “didn’t scream bridal.” Then and this is the part that broke me, she spilled her iced coffee right on the hem of the sample gown. She laughed and said, “Oops, maybe it’s a sign you need something else.”

I held it together at the shop, but I sobbed at home later. When I told my fiancé I didn’t want her as a bridesmaid anymore, he said I was overreacting and that she didn’t mean it maliciously. He’s worried it’ll “cause drama.”

I feel like if someone actively undermines me on one of the most stressful days of my life, I shouldn’t have to pretend we’re close for photos. But now I’m wondering if I’m being the ahole by potentially fracturing his family dynamic before the wedding.

Here's what people had to say to OP:

Capital-9 said:

Fiancé should be handling his family. If he doesn’t, he is not supporting you.

No-Daikon3645 said:

If your fiancé doesn't have your back now, you really need to understand this will be your life forever, him constantly putting her before you.

Equivalent-Bug1798 said:

NTA. She literally damaged the dress and if it was a sample then she damaged the bridal store's property which she ought to be held accountable for, or if it was your dress that you bought and paid for, she damaged your property and should be held accountable for! If she's pulling stunts like this now, imagine how she'll be during your actual wedding? No room for assholes in the bridal party.

grayblue_grrl said:

"He’s worried it’ll cause drama." Who would he rather upset? You or his sister and maybe her mother? BUT why did you ask her to be a bride's maid at all though? You knew what she was like.

Only_Bumblebee_1032 said:

NTA. Bridesmaids should be people who lift you up, not tear you down. If your fiancé is more worried about “drama” than your feelings, he should be the one to manage his sister’s reaction, not you.

EggshellsShoelaces said:

NTA. If your fiancé can’t support you in moments like this, what’s going to happen when you have kids and his sister pulls something? You need his hundred percent backing on these things or I wouldn’t go through with it.

Because it could be a lifelong problem that you don’t wanna deal with. I would suggest couples counseling to discuss the situation with his sister and how best to resolve it.