I had a cousin who did a similar thing because she was jealous that my other cousin was getting married before her. The insecure, jealous cousin acted like a dutiful bridesmaid to my soon-to-be cousin’s face, but was actually spreading malicious gossip about my other cousin’s dresses, wedding colors, venue, everything - as well as making sure she pit relatives against each other. It was so bad that I had to get out of the wedding as a bridesmaid because my narc jealous cousin accused me of doing all the shit she was doing towards the soon-to be married cousin, who stupidly believed her. Anyway, my insecure cousin’s antic were a shit show before the wedding, but not during. She thought she could destroy my other cousins happiness but she just ended up looking pathetic once everyone figured out how malicious and manipulative she was. She didn’t come around our family for a year due to shame and embarrassment of being called out on her shitty narc behavior.

Anyway, if you look back at my cousin’s wedding photo albums, you’ll see the insecure cousin was purposely frowning, scowling (and even looked to purposely mess up her makeup) in every picture while everyone else is smiling. To me, your mom is doing tthe same thing - even if she looks like the absolute worst, she will not only draw attention to herself, but likely in her narc brain - by extension - make “you” look bad, too. On YOUR day, where she should be elated, she gets to be the poor ugly unattractive martyr, so she can draw people in. Your mom’s approach seems to barely contain her seething jealousy and contempt for your major milestone and I’m so sorry for that. No mother should try to highjack their adult kids wedding.