Supernatural fans probably still remember Lauren for her character : Bella Talbot, a mercenary who screwing up the Winchester brothers several times. She has a love-hate flirtation with Dean and appeared on Sam's wild, dirty dream. The short is, she made them wet and angry.
Well, I don't know how the situation will differs (or same) but Lauren Cohan will play a new vampire in the town, Rose. Source confirmed and described that Rose is over 500 years old and disarmingly elegant despite a "tough girl" first impression. Five centuries of bloodsucking have given her a certain edge. "Maybe there's some humanity left in her -- have fun finding it," the source says.
There are several questions : What her relationship with Katherine? Is she enemy or friend? Will Rose screws up the Salvatore brothers just like Bela did to the Winchester brothers ? Well, we have to wait for episode 8 "Rose"