AITA for not telling my niece the extenuating circumstances that caused her prom dress to be used by another girl at the same school?

My niece goes to the same high school I did. It's a comprehensive school with about 1500 students. She was looking forward to going to the senior prom and wanted a custom made dress. She went to a local dressmaker. It's a family business with a mom and two daughters who all sew. They make everything; wedding dresses, clothes, costumes, accessories. My niece told them she wanted a custom prom dress, described what she wanted, they took her measurements and she ordered the dress.<br><br>Then the girl who runs the soccer team wore my niece's dress to the junior prom. The dress maker had taken the order, made the dress to my niece's measurements, and then sold it to another high school girl and was making a new dress for my niece. My niece was angry and felt betrayed. She went to the dressmaker who said she was so stressed out by her daughter getting covid that she sold my niece's dress to cover the lost income from her daughter not being in the shop for two weeks. She offered my niece a discount and they offered to let my niece come up with a new design and make two dresses, one for now and one to keep for later for free.<br><br>I thought it was a fair compromise but my sister insisted that the dressmaker tell the other girl where she got the dress and ask her if she would give it back to my niece. I told my sister that nosing into the lives of high school girls by asking one girl to give back her prom dress because some other girl felt entitled to it was just too much and would cause a lot of drama. My niece agreed with me and said she wanted no part of that kind of thing. She decided on a new design and the dressmaker and her daughters made her two beautiful dresses. They delivered them to our house the morning of prom.<br><br>My sister was angry that I supported this and said that I should have gotten my niece "her original dress back." My niece had a great time at her prom and liked her new dress. This was May and prom was in late May. The problem came up again when my sister and her husband came to my house to look at my niece's prom photos. My niece and her friends were taking some pictures at the park and there was a girl in the background wearing the "stolen dress." My sister said some not nice things about the girl in the dress and my niece said it was the girl from the soccer team. My sister said "she had no right to wear that dress and she's just a thief." My niece said she had nothing against the girl and felt bad that there was so much drama. I agreed with my niece and said it made me angry that my sister kept going on about this girl who did nothing wrong. My sister said I was taking my niece's side because I always hated her. I said that was bullshit and I did not hate her but I did hate that she was so obsessed with drama.<br><br>My sister said that if I hated her so much I didn't have to let her and her family come over all the time. I said she was the one who always showed up at my house uninvited. She left in a huff taking her husband and daughter with her. She's been giving me the silent treatment and so has her husband. My mom says I was wrong to not help my niece get her "original dress" back. My brother says my niece should have just worn a different dress and gotten over it. I think my niece and I handled it the right way. AITAA?<br><br>&#x200B;