I really dislike my sister’s best friend

So as close as it comes to hating someone, is basically how I feel about my sister’s best friend. To preface, my sister and her friend are both 25 and I am 30. She has had a history of being problematic towards my sister. For example, being jealous of her other friends and creating drama to try and alienate her. Also ridiculing my sister’s boyfriend (now fiancé) to her face out of, you guessed it, jealousy.

This all started yesterday, at a get together my sister threw for galentines. She’s recently engaged and the people that came are in her wedding party (myself included). I am already married so she wants me to be her matron of honor and problematic friend be the maid of honor. The entire night she drank and grew obnoxiously loud while the rest of the party had no alcohol. She made a comment about me looking heavier and needing to watch what I eat before the wedding (to which I ignored because I’m non confrontational and the night was about my sister). When discussing the upcoming bridal shower I told the party that since I’m not participating in games (because it wouldn’t be fair to everyone else), I’ll be handing out gifts and running the games. Friend became very angry and passive aggressive for the rest of the night after this. The night concluded eventually and everyone else was in high spirits apart from her friend.

The next morning she apparently messaged my sister saying I was rude, made her feel uncomfortable and ruined the vibe of the entire night. There’s no issue between my sister and I because she knows that wasn’t the case but with her wedding coming (July) and me helping her plan I’m going to have to deal with her brat of a friend and I truly can’t stand her.

My sister is an adult, I don’t have a say in who she chooses to keep in her life and she’s sensitive so I support her as much as I can without trying to upset her. So I don’t want to start a big deal about her friend’s shitty behavior but I also don’t want to put up with her bs for the months to come.