Sue Carson was a character of The Vampire Diaries novel series. She was one of Bonnie McCullough, Meredith Sulez, and Elena Gilbert's best friends since childhood. She was also a student at Robert E. Lee High School.
The Original Series
Sue attended Elena's funeral with her father and brother Doug was witnessed the attack to the dogs on the town. She later thanked Stefan for running in and saving her brother from the dogs' attack.
Caroline threw a surprise party for Meredith's eighteenth birthday, inviting Sue and, reluctantly, Vickie Bennett. In the middle of the party, Sue expressed her grief over Elena's death. Bonnie told them all of the dream and they decided to contact Elena using an Ouija Board. Elena warned them that evil was in Fell's Church and that they had to get out of the house. The girls panicked when the lights went out and Sue and Vickie were separated from the others. Bonnie and Meredith heard Sue's frightened pleads from the living room before hearing her scream. The lights went on and when they went upstairs, they found a hysteric Vickie near the window, with Sue broken body outside.
Matt Honeycutt, Bonnie and Meredith summoned Stefan to help them find this evil that killed Sue and when Stefan examined Sue's body, he found a cut on her that vampires made to exchange blood, but Sue wasn't a vampire. His researched revealed that Sue was killed for a blood ritual so Tyler Smallwood could awaken the werewolf gene inside of him.
The Return Series
The Celestial Court revived those killed by Katherine and Klaus. One can assume that she, Vickie and others killed by Klaus and Katherine came back to life.
The Hunters Series
In The Hunters, Sue Carson, the girl Tyler killed in order to become a werewolf, is alive, and it is questioned if Tyler is still a werewolf or human. He is mentioned throughout the first book numerously (Phantom) and it is said that his parents aren't the least bit worried about his disappearance and that he will come home when he wants to. Caleb Smallwood, his cousin, comes to Fells Church to find out where he went.