Should I listen to my parents or my therapist?

I really love my parents, but even though I'm nearly 20 they still have a lot of control over me including how I dress. I'm attending an event with them this weekend and I really want to wear a suit because I'm a trans guy. My therapist told me I should tell my parents what I want to do especially now that I am an adult. However, when I brought up wearing a suit with my mom she got upset and said I should wear a dress because I have so many, and they look good on me. She also said she didn't want me to embarrass her in front of her co-workers since this is a charity event put on by her work. I don't know if I should listen to my therapist, wear a suit and potentially make my parents upset. Or if I should suck it up and wear something I hate for the evening to make them happy. I hate conflict but I also don't want to be miserable dressing like a girl. Please help!