Gender identity and relationships

Thanks in advance for sticking with me through this long explantion. I've just recently began to come to terms with my gender identity. I've known for some time who I am, but I'm only now accepting it and trying to inform myself that I'm valid. I'm biologically female and I've been known to either wear sweatpants and a tee in public or long dresses and skirts. I've overcompensated to fill my gaping whole of femininity by presenting myself feminine. Now, it's beginning to eat me alive. I'm repulsed by the thought of a tight shirt because my breasts will show or any of my pants that fit well around my curves. The only person I've told and discussed my gender with is my fiance. She's incredibly supportive and accepting of me and she's beginning further understand who I am. I've been wearing as masculine as I can get to without making myself obvious. It's a very sensitive topic I don't want leaking about to my family and friends. My lifelong best friend has just invited me to her birthday celebration and she's asking that I wear a fancy dress and doll my face up so she can have a photoshoot (She's a photographer). I asked her if I had to wear a dress and she very strongly wants me to. I don't know if I should do it to make her happy for awhile and myself upset for awhile or vice versa. I'm sorry this was so long, but I truly need some advice.