My future SIL has mentioned several times that she would like to be part of our wedding. She wants to be a bridesmaid. I explained to here that I had already chosen who would be part of my WP. My fiancé doesn't have many close friends, so he chose four friends/family and I chose four of my closest friends/family to be in our wedding. My fiancé is trying to convince me to let his sister be a BM. If I had a choice on who to add in my wedding it would be another one of my girlfriends. How do I nicely break it down that I do not want her in my wedding party? Our wedding is more than a year away and I have to deal with stuff like this.