I usually just call everybody "he" because I've actually never seen the point of gender-different pronouns in any language. I'm hoping at some point in the far-distant future society will drop them entirely. "He" is marginally shorter, and I am male myself (I always imagine people with unknown demographics as being like me).
Usually, the way to tell actual female gamers from fakes is their unobtrusiveness (as well as spelling and being a constructive member of the community). The frauds usually claim to be female with a statement along the lines of "W000T YALL: IZ A CHICK!!!!!11!!!!!!!!!!!! I CAN HAZ FONE NUBMER??", while actual women are more often revealed by statements like "BTW, I'd appreciate it if you'd stop calling me 'he'" three pages deep into a discussion. (I am exaggerating somewhat here, but you get my point)
But over all, does it really matter? Well, yes it sort of does from a social inspection point of view, because I'm very interested in tracking both the integration of women into mainstream society and in demographic trends among game/computer nerds, but really from the perspective of the game I couldn't care less. What matters is that they focus and contribute.