My(F27) future SIL(F25) is accusing me of being racist over a wedding dance.

So my wedding will be an intercultural wedding that incorporates a lot more of my culture than my fiance's. I am African(actually african)-American while my husband is just American. My wedding is this upcoming winter and my bridesmaids and I have started practicing the wedding dance. Here is a link to give you an idea of something we are doing: https://www.youtube.com/watch?v=oYIcNYG4_Og&ab_channel=BenProRecords

We are having 7 bridesmaids and 1 of the bridesmaids is my fiance's sister. Everything was going totally fine until we started practicing the dance. I have changed the dance 3 TIMES because she kept complaining about certain moves, and after 2 sessions ago, she requested that I make it even more simple , and this time I denied to do so.

Then we had last week's session. The other 6 members of my wedding party tried their best, but she was complaining the time. She wasn’t even trying, she’d just automatically say that she couldn’t do a certain move. One of my bridesmaids called her out for complaining , and after that she was quiet. Right after, she texted me this long paragraph that she can’t be a bridesmaid. I simply replied “okay”. A week goes by and I wake up to this message (blanks are names). For those that can’t open it, she said that she feels like we were treating her different because she was white and thinks that we’re talking about her whenever french is being spoken. She also said she didn’t appreciate the fact that I simply said “okay”.

At this point, I’ve moved from annoyed to pissed. She is expecting me to fight for her to be apart of my wedding I honestly feel that she is trying to create an issue out of nothing because she feels uncomfortable. I get being uncomfortable, but her trying to pin it on race is outlandish. I wouldn’t be marrying her brother if that was the case. Where do I even begin to respond to this ?