I don't want to put too much distance between us, but I'm 26 (male). I personally am never surprised when I run into a female gamer, and I make it a point not to assume anything until I know for certain. It might be something that's more common in my generation, or I might just be one of the few.
I was raised to believe that men and women both have their own strengths and weaknesses, and there are several things that both genders can do equally well. So when I see a female gamer playing the game intelligibly, it comes as no surprise. As far as I know, the game isn't gender biased (although I can't really speak from a female's perspective), so other than considering existing 'social taboos,' there's no reason to have this mentality with female gamers anymore.
Yes, in earlier days video games were male dominated, and even today it is to a degree. But females are quickly balancing the scales with time.