I want to preface this to say that I know what I’m about to share is the norm, but:
My ex-girlfriend openly (to me) said she only participated in Magic the Gathering for attention. She had an ex (who is now a friend of mine) who really liked Magic the Gathering, which she really hated. Sometimes he would be in the middle of a Magic game with a friend in his dorm, and she’d walk in and ask him to do something for her. If he said “after this game” she would go down the hall and find a mutual friend to cheat on him with, and then tell her ex about it in detail to teach him not to play Magic when she needed something. She didn’t do this when he put off a request for anything else, just Magic. And no, ignoring her for Magic wasn’t a regular problem – she openly admits this only happened once or twice, she just wanted to punish him for Magic.
That said, she always went to tournaments and game days with him at the shop. Why? Because she liked how easy it was to get attention from people there. She was the only girl there, and she’s reasonably cute, and she liked the fawning, and she liked flirting with all of them to make her boyfriend jealous. She still hated the game, but she would play sometimes just so people would fawn over her playing Magic. I’m not inferring any of this, she outright told me.
Now, I wouldn’t call my ex a “fake geek girl” (albeit she didn’t even self-identify as a geek in public or otherwise), she was pretty obsessed with anime, and likes World of Warcraft, but she was almost certainly a “fake Magic player.” She was pretty, but insecure, and not quite pretty/confident enough to get anyone she wanted. She found geeky guys to be easy targets to seduce compared to non-geeky guys. She openly said that she hates most geeky hobbies that aren’t anime, but proudly admitted that she would feign interest in them to get attention.
Now remember I don’t this is an epidemic and my ex was kind of fucked up, but it has happened with at least one person. And yes, the problem is in large part from geeks putting women up on a pedestal, but I would be surprised if there weren’t a couple of insecure cute-but-not-supermodel girls with a pathological need for attention who realized that geeks are easy targets.
That doesn’t mean that we should start a witch hunt for fake geek girls. That doesn’t mean I don’t take girls who say they share certain interests at face value. I think there are fake geek guys too. I really don’t care, I want people to do what they like and be happy without worrying about whether somebody else accepts their self label or not, but I don’t think it’s inconceivable that people who may be insecure or screwed up in certain ways might feign interest in things just to have a place of belonging or safety or fulfill certain pathological needs. It’s almost certainly very, very rare though, because it takes a certain perfect storm of mental issues to get into scenarios like that.