Buffy Sanders (portrayed by Brooke Nevin) was a minor antagonist in Smallville, appearing as the "freak of the week" in the Season 5 episode "Thirst". She was the head of Metropolis University's Tri-Psi sorority and possessed vampire-like attributes which she had gained via kryptonite exposure.
Six years before going to Met U, Buffy was a resident of Smallville and had, at one point, found herself trapped in a cave inhabited by vampire bats. The bats had mutated after being exposed to kryptonite and, after biting Buffy, infected her with rabies. The kryptonite had altered the virus in the bats' saliva, causing Buffy to take on a number of traits attributed to vampires in myth and folklore, including enhanced strength, speed, heightened senses, accelerated healing, and an aversion to sunlight. Of course, she also developed cannibalistic urges and began feeding on human blood.
In 2005, Lana Lang moved to Metropolis to attend Met U, applying to join the Tri-Psi sorority. Buffy and the other sorority girls took a liking to Lana and allowed her in, but turned her into a vampire like them by having her drink their infected blood. At this time, Chloe Sullivan was searching for a story to present to Pauline Kahn at the Daily Planet and began looking into Tri-Psi. She discovered that ever since Buffy had joined the sorority, none of the girls had ever left.
Later, Chloe and Clark attended a Tri-Psi Halloween party to find Lana, who was caught by Chloe dancing a little too close with another guy. She confronted Lana about this and Lana bit her, but Clark came to her rescue. Buffy saw that Clark had seen Lana bite into Chloe and threatened to have the sorority feed on Lana unless she brought Clark back to them as a meal. Lana succeeded in doing this by biting into Clark while he was visiting Lex Luthor and in the process gained his strength and heat vision. Later, when the sorority sisters were about to feed on Clark, Lana stopped them, saying that he was not a normal guy and suggested that they turn him instead. This angered Buffy, who faced off with Lana, but Lana promptly incinerated her with a blast of heat vision.