AITA for picking a “revealing”bridesmaid dress in order to get one of my bridesmaids to drop

So this has been a long thing coming. My soon to be husband has a sister let’s call her Mia. Now Mia and I do not click very well. I am polite but I wouldn’t say we are friends. I felt I was forced by his family to make her a bridesmaid or she will be sad.

I am going to be blunt, Mia is fat and very insecure about it. This has led bridesmaid dresses shopping to be a nightmare. Never could find something she wants and all the other bridesmaid and me liking it. So I gave everyone two options to vote on. Option one was getting a dress that can be styled multiple ways, or picking from a collection so everyone matches but they will need to pay for it. Option two was I will buy everyone’s dress but what I chose the dress and my decision is final.

My five bridesmaids voted and options two won. So I picked out a blue strapless dress with a mini slit. I really like it and I knew Mia would have an issue with it. I sent a picture to all the bridesmaid and confirming the right size before I ordered it.

This is where it blew up. Mia was pissed I picked a revealing dress. This resulted in an argument where she thinks I am a huge jerk and I told her she can step down if she has issues with the dress.

She tried to get the family on her side but everyone knows I gave them options and had watched me struggle to find something everyone wants.

Edit: she voted for the option where I pay for the dress. I truly didn’t ask her since her and MIL announced she was one of my bridesmaid at a family gathering. The only way to keep peace with the whole family was basically giving her what she wanted.

I also have gone to 4 different shops to find a dress for everyone.