Oh Joss, you suck. Who the hell knows if the demon-essence part of the Slayer is in all the potentials and only gets awakened in the Chosen One or it enters her when the previous one dies or WHAT.

I'm fine with just human, or just really in shape human with a pierced tongue.

OTOH Illyria would know what a Vampire Slayer is, so if the Potential thing ever comes up, she'd get it, at least.