I posted this morning about relationship dynamics of the issue, I don't wish to go back on that train, although I do conclude with the same point.
The very definition of "nerd" seems to be what this thread has degenerated into. To some people it seems to mean a dedicated devotion to a singular thing, and to others a very broad array of interests in activities that are classified as "nerdy". It would be very difficult for any person male or female to existed in both groups simultaneously. Either you dedicate yourself to knowing something inside out, to learn every facet of something, or you cherrypick a few things that you adore and know a lot of other stuff in passing. I am a hockey and WW2 nerd in the devoted category, but perhaps only a "fake nerd" to hardcore gamers or Anime junkies. I can't name every game on every platform ever made, let along have the time (and increasingly the finances) to play them all, but there are some people on this forum that do know and have played the vast majority of those games. The expectation that every female game nerd needs to know as much as Jim Sterling or every female movie buff needs to know as much as Movie Bob is the type of scrunity that is unfair. The issue I have with the grilling of the female nerds (legit nerds, not "fake") is that they are often held up to an impossible standard even if they are really knowledgeable.
Here's my example to help illustrate my overall point.
I love Star Trek, have seen every episode of every series, all the movies, I'm sure there are plenty of posters who have as well, but if I was in a place having to debate semantics of individual episodes withour reference to what happened in that episode or argue over the racial characteristics of the various races, to that group I will not be considered "nerdy" enough. I am not in a position of authority on Star Trek, but some people are walking Gene Roddenberry's. It depends on the level of interest.
To the Gene Roddenberry's I'm probably considered a poser, but to society at large I am a Trekkie and proudly so. I may be scoffed by the Gene Roddenberry's, but a female Trekkie would be expected to know the episode number in TOS where James Kirk's grave was improperly marked, whereas I can get by simply knowing that it occured.
There are sports "fans" that can't name the team that won the championship last year. There are "video game fans" that think 5 hours of gaming in a row is a marathon. There are Battlestar Galatica "nerds" I've met that don't know there was a 1970s Battlestar, Starbuck was a man, and Gaius Baltar worked directly for the Cyclons. Everything has it's elitists, hardcore fans, casuals, and posers.
As I allude to in my first post, it seems "Fake Nerds Girls" seemingly only exist in the eye of the beholder. Every sports, hobby, game, activity has it, I don't see how video games are different.