Throwing this out there but a little twist on that could be she SEES everyone/some people as vamps/horrible monsters, even though their not? I mean, granted, a simple "NO SERIOUSLY STOP I SWEAR I AM NOT A VAMPIRE YOU'RE GOING CRAZY" could fix things, sometimes. But if she actually SEES the fangs and "grr" face and eyes and evilness and whatnot? Her instincts might prevail and it would cause some other Taxon members to actually have to run away and deal with Buffy hunting them and maybe if you wanna get real dark, hurting someone. Kinda reminds me of that episode...crap, I can't remember the name. The one where she thinks she's back in a psychiatric ward and her world as the slayer is all in her head.

So yes I'd definitely like to see Buffy in full on slayer mode!