AITA for harbouring some resentment over my role in a wedding?

I’ve been a bit scorned from some weddings, as far as invites (or lack there of) and my place in the wedding. I’ll start with this one, and of course, I understand that it’s not my wedding and the couple getting married can do whatever they want.

A couple of years ago, my best friend got married. Her and I have been #1 with a bullet, ride-or-die besties for over 20 years. Since I was her closest, longest friend and she didn’t have any siblings, I kind of always expected that I would be her MOH. I should mention, too, that we’ve always been close. It wasn’t like we were school friends and then drifted apart - no. We stayed best friends, lived by each other, travelled together, travelled with our families, played on sports teams together… very close.

When I got the invite in the mail asking me to be her bridesmaid, I was gutted. Bridesmaid? In that moment, I really felt like I held our relationship in higher regard than my friend did.

She had decided to make her future sister-in-law her MOH. I can kind of connect the dots on this…they were close, and that SIL is the reason why my friend met her husband, sure.

Here’s the thing though, I remember when my friend and her fiancé (now husband) first started dating, this SIL was VERY vocal about her distain over their relationship. She was extremely uncomfortable about her friend and her brother dating and she let everyone know it. If I’m remembering correctly (because my friend who got married told me all this), I think the SIL even sent out a mass email to the family expressing her discomfort over their relationship.

I just could not believe that I was snubbed out of the MOH position for someone like that. Absolutely heart broken.

So, 1/2 questions:

Am I overreacting? Or do I have every right to be extremely pissed off over this? I still went to the wedding, smiled for the pictures, helped where I could, but our friendship definitely has a different heaviness to it.

2/2

Is it weird that the SIL happily agreed to be the MOH? Maybe she’s the asshole, lol. As far as I know, she didn’t even question being asked to be MOH. And, on top of her initial issue with the couples’ relationship, she also knew that the bride and I were very close. I just think that - if it was me - I would have stepped aside? But obviously I’m biased. It just seems a little short sighted to me.

Thanks for your input!