Charlotte West was a powerful witch until she was killed and turned into a vampire. She is also the girlfriend of Henry Knight and was previously a
When she turned into a vampire, she lost all of her natural witch abilities with no way to turn back into a human or witch. Henry and her searched for many spells, looking for a way to change her back, but there was no way and she killed multiple humans with her lust for blood.
However, these temptations calmed down with the help of another vampire (maybe Stephan or Arianna). Even though she was immortal, Henry and her still spent the rest of their life together.