That % must be pretty old. Entertainment software site - 2015 - 44% women. Consoles have brought more of us into the gaming world and once they get in with the consoles it's not a far jump to add a game to your pc.
Also depends on who does the survey. But the point is women do play video games and if the developers want to dip into that payload they need to make them aware that not all games are about Snake, Tidus or even Zelda.
Don't know how old you are or even if you have or want kids, or maybe you don't want any daughter you may have in the future to be a gamer but I would like BioWare in particular, to get as many new gamers as possible.
Pretty much any statistic on the matter is going to be unreliable at best.
The one from BioWare is that 18% of people played femshep, not that 18% of players were female. Any guy playing as femshep is part of that 18%, and any girl playing as broshep isn't.
Even other stats as to "how many gamers are women" more often than not seems to include games on social media like Facebook, which is hardly a demographic that has any value in being combined with hardcore gaming. Even if you manage to not include that, then it's bound to vary from genre to genre.
It's anecdotal evidence at best and thus equally as unreliable, but my experience is that FPS is more predominately guys while RPGs aren't as much so.
Of course I would also say that these days people shouldn't be buying a game just off promotional material alone. You should look up what kind of character creation options you're going to have in a game if it seems interesting. Dismissing a game simply because it's got some grizzled white dude walking away from the camera on the cover(you specifically may not do this, but it's been mentioned in this thread) seems as silly a notion as companies thinking that they need to keep doing that.
Seriously, what is it with the grizzled white dudes walking either away or towards the camera?