Future mil drama

Hi everyone. I have a question regarding my fiancé’s dad’s wife. A little background. This is his dads third marriage. His dad had an affair with my fiancé’s mom when my fiancé was a teenager, and has since remarried twice.

My fiancé just calls her by her name and does not refer to her as step mom or anything. He says he merely tolerates her to keep a relationship with his dad, which he did not have for a long time after the divorce.
His dad and wife have been responsible for planning our rehearsal dinner. They initially both said they didn’t even know this was the grooms family’s role, and had to Google everything. They have failed to keep me in the loop about any of it, and the wedding is in my hometown and I was happy to offer help. They wouldn’t even tell me the caterer without me having to ask multiple times.
My family and family friends have a long standing tradition of throwing an after party for the couple after the rehearsal dinner. This was something I didn’t feel like I had to have, but 10 of our closest family friends really wanted to throw it for us and for out of town guests not invited to rehearsal to have something to do, so I said of course why it. This upset his dads wife, and they have since asked multiple times if we even want the rehearsal dinner (last time was this week) even though the wedding is literallly in 1 week.
All that is whatever, and was annoying but didn’t piss me off. What has made me upset is that his dads wife has been emailing my family members and friends from the rehearsal dinner list and uninviting them without coming to me first. My cousin was uninvited even though he is 35 years old and has the same last name as me, but because he was listed as the child of my aunt and uncle (because he is…) they emailed him saying “I don’t know what the bride (insert my name) told you, but children are not allowed.” They also emailed my bridesmaid this even though her daughter is my flower girl. She never once asked me who these people were or if we could trim the guest list. The list has 1 more person than anticipated, but less people are actually eating because I have family members with special needs/allergies that are leaving early, and just stopping by to say hello.
It’s all really hurt my feelings. I’ve tried to communicate with her but she always leaves it short or passive aggressive. My fiancé hates talking about it because he doesn’t like her but doesn’t want to have conflict with his dad. This in turn causes conflict with our relationship. Am I wrong for being upset? How would y’all approach this? Thanks!