Should I allow her to tell me herself or should I say something?

I met this guy about a week ago and he asked me out on a date. He seemed far too young for me because he’s just really adorable with no facial hair at all and he basically looks about 14. I found out that he’s actually 22 so I decided that we could go out on a date. Something I realized halfway through our date was that he was indeed a she but it was impossible to tell because she has no breasts or feminine shape or anything. She looks like a he but my best friend, who knew it was a female, texted me and told me that this was a girl. I am bisexual so I don’t care but she has yet to tell me that she’s really a girl. She even told me that her name was Darren and I completely believed that. Not once has she ever referred to herself outside of being a man. Should I say something to her or just let her tell me in time?