I would have given the same advice had I known you were female. When one says "flirt" one presumes there's a little bit of sexual something there and that's all that matters. Boy/girl, girl/girl, boy/boy, yeah, you "flirt" differently but the end result is the same. I've always presumed the "there are no girls on the Internet" works both ways - I've seen first-hand the amount of bullshit one has to put up with when one is a girl on the Internet. If someone does not say "I'm a girl" I presume they'd prefer it not enter into the conversation. There is wisdom to this. The internet is a long goddamn way from gender-neutral. Generally the best move is to be gender-unspecified. Amusingly enough, Redditors often think I'm a woman. There is a subset of humanity that apparently believes one cannot dispense advice in an empathetic fashion without possessing ovaries.