Something next to normal, that's the thing I'd like to try

Uh... I don't think I've ever written Buffy as using vanilla-scented anything. I usually go with fruity or occasionally flowery scents. I'm completely clueless about designer perfumes, so if you can't buy it at Bath & Body Works, my Buffy probably won't use it.

As for the fanon vanilla obsession, I think it stemmed from Sarah Michelle Gellar once saying in an interview that she used vanilla-scented something or other, and so some fans have adopted that as Buffy's signature scent.