Plenty? Yes, plenty of girls wear heaphones in the streets, on the bus, the train... no doubt it has become a fashion accessory (thx dr. dre...) and i find that sexy.
But do you mean that because we have plenty of ladies on head-fi there are plenty of girls INTO headphones in general?
Wearing a headphone and spending a lot of time with headphones are two different things.
Even the two DJ girls that I know don't give a shizzle about headphones... They do love their Senn HD-25 A LOT, but that's all, it's a workhorse.
There's no way they will buy other HPs, compare signatures, FR, presentation, visit head-fi, or even talk more than 5 mins about headphones.
oh, and that's true for 95% of men too... it's not specific to girls.
it is a NICHE