Buffy Sanders was the freak of the week in the WB TV series Smallville. She appeared as the main antagonist in the Season 5 episode "Thirst".
Before attending to Metropolis University, Buffy was a resident of Smallville and had, at one point, found herself trapped in a cave inhabited by vampire bats. The bats were infected with meteor rock-irradiated stalactites. After being bitten, she mutated into a metahuman with vampire-like traits and weaknesses and was eventually recused by LuthorCorp. Becoming an immortal vampire, Buffy developed cannibalistic urges and began feeding on human blood. When she went to Met U, Buffy became the president of the Tri-Psi sorority and it was defined as the best on campus, with the richest and prettiest girls.
In 2005, Lana Lang moved to Metropolis to attend Met U at the last minute and was forced to join a sorority to find housing at such a late date, applying to join the Tri-Psi sorority. Buffy introduced herself and group as the prettiest and most exclusive sorority to Lana and the rest of the pledges. After trimming the pledges, Buffy and the other sorority girls took a liking to Lana and allowed her in, much to her surprise.
Buffy tells her that there is one more initiation ritual, revealing they were all vampires and turned Lana into a vampire by cutting her own tongue and making Lana drink her blood with a kiss. During this time, Chloe Sullivan was searching for a story to submit to 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. They split up to locate Lana who was caught by Chloe dancing a little too close with another guy.
Clark ducked into a bedroom where Buffy caught him rummaging. She ordered him to leave, but she was distracted by someone at her door. When she turned back to Clark, he was gone. After the party, Buffy saw that Clark had seen Lana bite into Chloe and the other girls were mad at Lana for leaving a victim alive. Buffy tells her that Clark was snooping around and she has to clean up her mess by bringing him back so they can finish him off as a meal, or Lana will be the one they feed off instead. Lana succeeded in doing this by biting into Clark while he was visiting Lex and in the process gained his strength and heat vision.
Clark is able to grab one of the syringes with the antidote in it before Lana takes him back to the sorority house. The sorority girls lay Clark on the hearth of the fireplace and prepare to feed on him. Lana stopped them, saying that he was not a normal guy and suggested that they turn him instead. The girls explain there is no room for Clark in a sorority. Buffy doesn't care what Lana wants and when Lana stands in her way, she knocks her to the floor.