Basically, they are female drivers but we don't actually have a demographic of how many who play GT5, nor have demographics for male drivers. But they are female drivers out there.
Sadly I don't think there's many, definitely wouldn't be my gf that's for sure.
Seriously though, I think GT5 might be another one of those games where male dominance makes itself abundantly prevalent, sadly the world hasn't given females the chance to catch up with the males.