Callie Gallagher was the daughter of a circus owner Patrick Gallagher, and was a friend of the newly turned Vampire, Stefan Salvatore. Callie first encountered Stefan in New Orleans, where she soon befriended him as Stefan gained a job at the circus where her father worked. She helped Stefan and Damon Salvatore escape from her father by starting a fire in the circus tent. However, Damon noticed that she meant something to Stefan, so Damon stabbed her with a knife, and prevented Stefan from feeding her his blood. After Damon fled, both Lexi and her friend Buxton tried to save her, but unfortunately she tragically died.
It is unknown if Callie exists in the TV series, but it is highly unlikely, seeing as she has not been mentioned. But it is certain if she did somehow survive her attack from Damon, and saw Stefan again, she would definitely stir up some bad memories for Stefan. However in the episode Ordinary People, at a bar Stefan and Damon met a bartender whose name is Callie. Stefan drinks from Callie several times in the episode. It is unknown if she has a link with Callie Gallagher from the books.
Callie is of Greek origin, and the meaning is "beautiful, lovely".