Vampires could maybe have Evil (it's quite evil to suck blood.) or Athletic (vampires are said to be strong and muscular) or Irresistible (like Edward Cullen and his family: clever, perfect & stunningly attractive) or Hates the Outdoors (should explain itself), for example.
Fairies are prankster teens that never gave up their pranks. Childish, Rebellious or Insane, maybe? Or then something less traditional and more mischievous, liken in Kiersten White's Paranormalcy: Evil, Mean Spirited or Commitment Issues?
Werewolves are hunters, but I think they also care a lot for their cubs. Loves the Outdoors, Gatherer and Slob belong in the former, Family Oriented and Friendly to the latter.
Witches are often associated with cats, so Cat Lover could fit for them. Or Loner or Genius, since the witches of the fairy tales usually work alone and are often intelligent.
Mermaids could have Flirty, Loves to Swim or Dramatic.