you can spot a poser very quickly usually.
Anytime someone brings up games and says "yeah i play games" i tend to ask "what do you play?". In a sense i'm looking to see how in depth your are into it. If it's just Fifa/Madden/Call of Duty or Angry Birds/Farmville/Sims - well yeah you do play games. and by definition you are a gamer. but in the geek lexicon you would not necessarily be a 'gamer' as is the term often understood.
Being a geek is knowing and loving the minutia of the medium/genre that they love.
whether male or female, i've personally encountered both who say they're nerdy, but neither exhibit nerdy behavior or show any strong interest and knowledge in something.
If a woman tells me that they read comics, and then tells me that she really liked "Y: The Last Man" or knows Hush from Batman, that you know Iron Man can't show in Gotham, or name drops Grant Morrison. Then regardless of the persons point of views and opinions, the fact that she/he read, enjoy, and actually know what they are talking about - in my book - makes you a geek.
and i don't think it's a bad thing, to be a geek.
but i do think in the mainstream that the word geek/nerd has become very fashionable and to the mainstream public it basically means your smart, and what you will get is people misappropriating the term. Then there are the attention seekers, these people will always exist no matter what.
people who are posing, usually know that they are doing that for attention. Acknowledge that and move on. You don't even need to rebuke them, if they insist on posing to be a geek, they'll make themselves look foolish around other people anyways.
Now if it's someone who's sincere and wants to just spend time with you and your hobby, and they know something because there was that joke in Big Bang Theory about whatever. Be patient Just ease them in let em' have some fun.
being a geek is being part of a club, and we all pay membership fee's, we pay it by spending the hours enjoying the things we love, whether it's games, comics, sci-fi etc.
As for myself, in terms of things that i am very geeky about would be video games, reading history/politics/religion/biography/contemporary issues, Godzilla, comics, animation (Western cartoons). I love Anime, but i know very little about anime apart from some popular anime like Miyazaki films, Paprika, Cowboy Bebop and Ghost in the Shell (and no.. i don't mean like Bleach and Naruto).
anyways those are my 2 cents.