One of my personal favorites is "Lamia" -- from John Keats' poem of 1819. You can read about it here:
http://www.geocities.com/Wellesley/Garden/4240/lamia.html
The article also makes a comparison between the Lamia and Lilith -- and Lilith is another great name.
You seem to be looking for a feminine name, so here are some Romanian female names taken from *The Melting Pot Book of Baby Names*. As I'm sure you're already aware, Transylvania is an area in the northwest mountains of the country of Romania.
Alina (to soothe)
Brindusa (flower name, crocus)
Ecaterina (pure)
Elica (noble, kind)
Florica (the flower)
Irini (peace)
Lucretia (brings light)
Rada (joy)
Of course, the meanings of these lovely names don't sound quite so ominious or "vampirelike" at first glance. Until one wisely recalls that a vampire's survival in human society is dependant on deception.
-- Nanaea