I would hazard to guess that if 50% of the gaming population is female, and 50% of the games played are casual games, there is clearly no need to discuss them. When you are bored or frustrated you just stop playing Candy Crush, Farmville or whatever single player Nintendo hand-held you are currently into. At no point is the game legitimately "challenging" (or catass) enough to require a "solution" board ala gamefaqs or a discussion in a larger sense in terms of mechanics, plot (lol), etc. I am not attempting to deride, devalue or judge these discrepancies in any way, I just feel they are always glossed over in a rush to make the point that "girls play too lol!"
So if you were to assume that the overlap was rather high between the females and the casual/single player titles, then I feel that would be the most simple explanation. I always see that statistic thrown out and it just seems that just as young males love the mechanics and environments of crass multiplayer shooters, women would deviate elsewhere.
Also everything else that has already been said about attempting to penetrate obscure insular environments with their own made up lingo and memetic propagation.