If your looking for places to find girl gamers, your best options (from what ive learned) are:
A: Japanese produced games. Harvest Moon is almost a chick magnet. Everyone female gamer ive met has played, and enjoyed a Harvest Moon game. I think its because of how much more adorable and fun Japanese games can be. (Im not saying women ARNT into hardcore gaming, im just saying its slightly less likely from my own experience.)
B: League of Legends has a pretty large female demographic compared to other games. Its a competitive game, but the important part is, its VERY team based. And while id never say women cant be lone wolfs, from my experience, team games tend to have a larger female following. Ive met more women on LoL then i have in most other games combined.
C: Reddit. While it may sound like a joke, there are a lot of women on reddit. Chances are, if you go to a cosplay thread, your going to run into at least 2-3 women. (You could always lurk the "LadyBoners" subreddit. its literally a forum full of women fawning over good looking men. If you can clean up really nice and take a great picture, you'll probably find a woman willing to chat there.)
D: Anime Conventions/Renaissance Fairs. Id be lying if i told you i havent met/hit-on/got hit-on by women at a renaissance fair. I happen to have a really nice suit of leather armor then makes my butt look nice. And apparently, quite a few women find the "Naughty Bandit" type attractive (At least until they see my eating habits). And ive been to a few Anime Conventions. They go on everywhere, you just have to take time to look, and plan ahead.
http://www.animecons.com/events/ Just look ahead of time, and see about going to one. Even if you dont go to pick up babes (*cough hack* i mean, fine ladies....), you can still have a great time. And if you do go for the women, then just put on a smile and when they talk about a female lead, tell them how "Kawaii" you think she is when she isnt being assaulted by something evil.
Honestly, if your looking for a "Gamer Girl", your best chance is to make one. Not like that >.> freak.
Find a nice girl, who doesnt think "OMG VIDYA GAYMZ R 4 CHILDEZ", and see if you cant get a kinect or a rockband game (with 2 guitars. Thats the most important part). A lot of women who say they arnt into gaming have just never played with someone they like spending time with. My Wife barely touched games, really only enjoying older PSX titles from her childhood. I got Rockband 3 and a 2nd guitar, shes now neck deep into LoL. You just have to introduce gaming slowly, with things that are easily accessible. Heck, if you have a kinect, rent the new Starwars Kinect game, and dance together. Because nothing is more enjoyable then to see your partner is just as big of a failure as you.