WIBTA if I told my sister I would no longer be her bridesmaid?

I F30 have history with groom, we had the same friendship group in early teens and twenty(my sister did not knows them). This friendship group imploded, when I had to take my ex to court for a number of reasons reddit will not allow me to post. (I won in court and have restraining order).

During this time I suffered from ptsd and anorexia, it took a long time to rebuild my life. Some of the group took his side and were not happy I was taking it to court. F1 would repeatedly harass me blocking my car in, threatening me and turn up where I was, including my house at all hours of the night. In the end I had to tell her, I would also take her to court if she did not back off.

The wedding is this year I was asked to be bridesmaid and happily accepted. 6 months later I see a post that my sister has asked F1 to be a bridesmaid (she is still friends with groom). I feel disrespected and that I do not feel comfortable with this person. Please note the bridal party was meant to get ready at my house and there's no way F1 is setting foot in my house. I don't want to be bridesmaid but my parents say I should keep the peace. I will still go to the wedding and support my sister, but want nothing to do with f1. I am not asking my sister to choose, just that I want to back out as bridesmaid. So WIBTA for breaking the peace?

Edit

Sister and family know about history with F1!