When my wife use to play Unreal Tournament, she never let it be known she was a girl. Not surprising based on the reaction some people have along with the rampant sexism/misogynism. Now it's just Portal and Bejeweled for her.
That said, I think RO is ever worse when it comes to ratios, since it's a realistic(er) WWII military shooter. In the real world, I know LOTS of guys into WWII, but not a single woman.
As far as women playing RO, I do remember back in the mod days playing BFE with Kruschev (on the Soviet side of course). Women playing RO do indeed seem few and far between. I'm sure we'll see more as RO2 gets popular, but I wouldn't count on the ratio to change much.