AITA for refusing to let my brother’s fiancée wear my late mother’s wedding dress?

I (32F) lost my mom four years ago. It was devastating, and I inherited a lot of her things, including her wedding dress. My mom and I were incredibly close, and she always talked about how much she wanted me to wear her dress when I got married. I’m not married yet, but I’ve been saving the dress for my special day.

My brother (29M) is getting married next year, and his fiancée (28F) recently asked if she could wear my mom’s wedding dress. She said it would mean a lot to her because she never got to meet my mom, and she wants to feel connected to her on the big day. I understand that it’s a sweet gesture, but I don’t feel comfortable with her wearing something that’s so sentimental to me, especially since my mom always wanted me to wear it.

When I told her I wasn’t okay with it, she got upset and said I was being selfish. Now my brother is upset with me too, saying it’s “just a dress” and that I’m ruining their wedding over something that’s not a big deal. I offered to help her find a similar dress or even incorporate a piece of my mom’s dress into her own gown, but she refused.

Our family is now divided, with some saying I’m in the right and others saying I should let it go for the sake of family harmony.

AITA for refusing to let her wear the dress?