OP, I've read your updates now. This is one thousand percent to do with your weddings being a month apart. The exact same thing happened to me. We had got engaged first, and had not set a date, but then it ended up having to be a month before hers. He was in the Army and got deployed at fairly short notice. You do NOT want to go off to a war zone without being married. So we had to arrange it at quite short notice, and one month before was the only date available for both church and hotel in that area. I got the impression she really thought that we should have put it off until after his long deployment, and that if he got killed, sacrificing all the widow's benefits would have been totally worth her having the only family wedding that summer! 🤣
I do not agree with PP that a month is close. Close would be 7-10 days. And weddings are about celebrating your love. They're not meant to be about competition.
I asked her to be my bridesmaid, and she said yes, but was then so shitty about things that I fired her. And obviously I she didn't ask me to be hers. The whole thing was SUCH a shame, because we're the same age and over the years had been like sisters. We were even at uni together.
And she was never the same to me again. Over the following years, she played up so much until I finally snapped and now we are totally estranged. Haven't spoken for a decade, and I'm glad. Someone who can behave like that, you don't want them in your life.
And your dad just died last year, and she's still excluding you??? What a horrible, horrible woman! I'm SO sorry, OP. Weddings really show what people are made of.
I think if you disinvite your cousin, it will only cause a big family rift. And you want her there, anyway. I hope she can get over it - my cousin couldn't. I never realised how selfish and spoiled she was. She had two big brothers and they tried for a third because they wanted a girl. When she finally came along, she was treated like a princess her whole life.
This wedding strife is really, really awful, but sadly it's very common. I wish people would be more careful not to fall out over weddings, because in my experience it's something that tends to have permanent effects. Maybe it's because weddings are occasions with such significance. Perhaps your cousin will live to regret it.