I realize the title of this already makes me sound like the a-hole but please bear with me.
I already had issues with my brother and SIL before inviting them to my wedding but my parents insisted. So I sent them invites and spoke with my SIL over the phone to confirm that they were aware of the color theme (red and black) as they would be apart of the service and in the wedding photos. She confirmed they understood and said they picked out the perfect dress and suit. Perfect.
On the day of, I had a lot to do and hadn't noticed them come in yet while I was rushing to get ready. About 30 minutes before the service I noticed them out in the crowd. My brother was wearing blue jeans and a black T-shirt with a suit jacket, I expected nothing less from him, and then I saw his wife. She was wearing a red T-shirt and black and white plaid pajama bottoms.
I brought this up to one of my bridesmaids and she informed me that she brought an extra dress and would gladly lend it to her for the evening. I approached my SIL about it at first she rejected the offer saying that she was (2 weeks) pregnant and comfortable in what she was already wearing. I didn't want to be a bridezilla but every single other guest (some also being pregnant and further along) made an effort to look nice or at the very least didn't show up in pajamas. I very politely asked her again to change or I would have to have her sit with the other guests during the ceremony. She agreed to change and it seemed to have turned into a non-issue. The rest of the day was great.
But multiple times since then, she has brought it up. Telling me I was rude for asking her to change and saying that my wedding was trashy anyways because it was held at a park (in an indoor building) so she felt that she shouldn't have needed to change...
So was I being a bridezilla? Was I wrong to ask her to change into something more appropriate for a wedding? AITA?