Faith from Buffy the Vampire Slayer and Kaylee from Firefly has something in common - both are very sexual women. But it's not just sexuality - they are both very sensual.
Food, for example. One of our early scenes of Kaylee involve her enjoying a strawberry (see the linked article). The "horny" part of "Isn't it crazy how slayin' just always makes you hungry and horny?" get the most attention, but "hungry" is just as valid.
But the two characters' sexuality is portrayed very differently: Kaylee's portrayed in a positive light, while Faith's is that of a "bad girl" and connected to her fall into darkness.