There are two kinds.
There's the girl gamer, and the gamer girl.
The girl gamer is the one that acts like a girl ahead of acting like a gamer, and is generally as portrayed above. They abuse the shock value of being one of a very small demographic to gain attention.
I've got Schizophrenia. That makes me part of a very small demographic! WEE! LOOK AT ME!! I'M DIFFERENT AND SPECIAL!
In a nutshell, annoying.
The gamer girl is the one that actually enjoys playing games, and doesn't make any attempt to throw to the fore the fact that she is, in fact, a girl, allowing other people to take note of this obvious fact themselves.
This is the kind that most nerds wish they were dating, myself included.
Pity they're a small percentage of that small demographic >.<