Nightmare fsil

In my fiancés culture, the MOH and best man are supposed to be a married couple. We don’t have very many married friends, and we were close with his middle sister and her husband at the time we planned our bridal party so it seemed obvious we should ask them. They were very happy when we asked them and agreed to take on the role. I have 6 total bridesmaids including my fiancés oldest sister who is recently divorced. I am purchasing all of the bridesmaids dresses, except for his two sisters as they insisted they want to buy their own so they can get something very nice and expensive. I’m totally fine with this because our wedding is black tie and the other bridesmaids will be wearing elegant gowns as well. His middle sister (MOH) has become a huge pain in the a** as we get closer to the wedding and she also started to have a problem with me because I asked my fiancé to cancel all of the credit cards he allowed his sister to open under his name when they were living together. While he has the money to pay for the cc and treat his family, I let him know it’s not ok for them to have unlimited spending access under his name and very irresponsible on his end. He agreed and spoke with her about cancelling the cards and not treating her to so many things moving forward. She is married after all and I feel this is an extremely weird dynamic. I know she has been bullying and abusing my FH because he is a pushover and he is finally finding his voice to speak up and say NO when it is appropriate. I’m going to list out all the things below so this post doesn’t get too long:

-my parents are paying for the bulk of our wedding but my fiancé is taking care of the florist so we can do something very nice. She keeps telling me she will plan the flowers (with absolutely no experience) because we shouldn’t spend so much. She is aware this is the one thing my fiancé is paying for.
-refuses to look at MOH gowns in the correct shade. I chose a deep red color for all of the bridal party gowns and she keeps showing bright red options and trying to convince me she could wear a different color because she is MOH. My cousin bought her dress first and showed my fiancés family, the sister said oh it’s nice but she is going to get something even better because she is MOH. -she is bringing her husband and their children to my bachelorette because her 3 year old can’t sleep without her. She did not clear this with me prior and I would have urged her to just stay home if it was going to be too difficult. I find this extremely strange she invited them without asking.-the oldest sister started dating someone 1 month ago and our wedding is in 2 months. The middle sister told me (not asked) that the oldest sisters new boyfriend is going to be in our bridal party. I told her absolutely not and she said well the older sister won’t be in the wedding then. I told her then so be it I’m fine with that. My fiancé absolutely does not want the new boyfriend in his party and confronted the oldest sister about this. The oldest sister had no idea the middle one was even suggesting this and she agreed it would be weird to ask her new boyfriend to be in our bridal party. To be clear, he is still invited as a plus one he just won’t be standing up at the altar with us. The middle sister and my fiancés mom told us we are rude for not changing the bridal party to allow the new boyfriend.-I told the middle sister we extended the dates of the bachelorette by one day if she would like to stay longer with us (prior to knowing she was bringing her entire family), she let me know her and the other sister planned to go bridesmaid dress shopping the same day we got back from the bachelorette. They never let me know about this shopping date which is extremely rude in my opinion as I have made an effort to be inclusive with them by inviting them to be in the bridal party and to all of the events. -my fiancé called the oldest sister to let her know that it’s not okay they planned this without me and they are not going to be picking their dresses without my approval. The oldest sister let him know the date was not set in stone and she agreed to change it so I would be able to make it. I texted them as well and the oldest sister agreed we will all go together, however the middle sister never replied.
Also to add on, I have a wedding planner who is taking care of everything and my moms best friends planned my bridal shower so there is really nothing for the bridal party to do besides show up. I have a hard time asking people to show up for me so I’m not putting any pressure on anyone in the party. Everyone else has been great besides my one fsil. I am honestly not looking for advice I just wanted to vent. Thank you so much for your input if you have read this far! And congratulations to all of the other brides.