She was killed by Klaus in O Come, All Ye Faithful as a way to get back at Tyler for betraying him.
Carol was a member of the Lockwood Family and a member of the Town Council.
In The Hybrid, Carol, worried that all of Caroline's friends might be vampires as well, poured vervain into the carafe of coffee the next morning to see if Tyler had also been turned.
Though Tyler definitely noticed something off about the coffee, he assumed it was just bad creamer and had no other reaction, which left Carol relieved that her son wasn't a vampire.
At the end of Crying Wolf, Carol found a note from Tyler telling her that he was leaving town with Jules, though, unbeknownst to her, he was leaving in order to learn to control his lycanthropy by joining her werewolf pack.