The interesting question is: how far can you diverge from what people think of as the "lore" before it stops becoming a "vampire"?
Back when I writing the Underworld
books, I used to run into confused fans who didn't grasp that the UW vamps didn't necessarily play by the same rules as, say, Buffy vamps or Anne Rice vamps or whatever. ("But vampires can't get pregnant! Everybody knows that!")
I do think, however, that if you're going to deviate from some standard bit of lore, you need to address that clearly and right away, just to avoid confusion.
"Contrary to popular legend, Selene could still see her reflection in the glass," etc.