Most of the girls that I know have played some sort of video game of some sort. And this is becoming a more consistent trend than in the past. In fact, out of everyone at work, the women were the most jealous of me that I got a DS, most of the guys were just like, eh, whatever... So while many women don't play the "mainstream" games that get all the hype necessarily, they are definitely playing something. Whether it's BrainAge on the DS, or RockBand, WiiFit, WiiBowling or any other various number of more accessible games, the trend is definitely solidifying in with the women gamers. I'm pretty sure that they'll never play stuff like Mass Effect or Crysis, and probably in a lower proportion of hours, but they're out there.
Think of it this way, out of the physical population, the 46 percent figure seems about right; out of the hours of gameplay logged around the world, I would say that men still log the significant majority, somewhere around 70 to 80 percent.