Closeted Butch Wedding Attires (What should I Wear?)

I am a closeted butch women who is trying to wear clothing I feel more comfortable and confident in. However, my sisters wedding is coming up, and my mother who doesn't know about my sexuality will probably buy me a dress.

I would love to attend the wedding in something I feel good wearing but I'm also worried about revealing my sexuality and/or being uncomfortable in myself. I won't feel like I'm being true to who I am but I'm also not trying to make a statement. This is her wedding and her day, I want as little drama for her as possible. Please, any suggestions for what I should do and wear?