Mom is transphobic and is letting me be a groomsman at a wedding when she thinks I'm a girl

I(15) am AFAB and genderfluid(boy right now) but I am closeted because my mom has transphobic views. A family friend is getting married and they have enough bridesmaids but not enough groomsmen so when she asks me if I want to be a bridesmaid, I said that I can just be with the groomsmen.

SHE AGREES. Then she says they can just get me a dress that fits the theme of groomsmen and I say that I can just wear what the groomsmen wear so I fit in. AND SHE LETS ME WITHOUT ANY QUESTIONS.

So I'm going to be labeled as a groomsman at a wedding, I will be with the groomsmen and I will wear the clothes groomsmen wear but my mom genuinely thinks I'm a girl

I would rant more about this but the conversation was short so there's not much I can rant about