I listen to a lot of singer songwriters and electropop, and there are a LOT more females in that corner ;)
LOL TVTropes even has a name for it (I read that entry yesterday): the Suzi Quatro Principle (meaning if there are females in rock bands they are always the singer or the bass player).

Let's see, some of my favorite females are
Martina from Dragonette (electropop and SO FIERCE oh my god)
Regina Spektor (sort of alternative singer-songwritery and so good)
Feist (my iTunes classifies it as either rock or alternative but I find her more singer-songwritery as well)
Kate Nash (pop with a twist)
Lily Allen (fiiiiiierce)
Yelle (electropop)
ROBOTS IN DISGUISE HOLY CRAP WHY DID I NOT THINK OF THEM UNTIL NOW they are so amazingly awesome, listening to 'Girl' always makes me feel that it's unbelievably awesome to be female

And atm I'm kind of embarrassingly into La Roux although I hated her at first.

So no rock, but enough amazing females in music anyway!