Sunday was a vampire who had been a UC Sunnydale student.
Sunday and her gang stalked their prey on the UCSD campus. They started by abducting their freshman dinner and quickly moved to clean out the victims' dorm room and leaving behind a note that said "I can't handle the pressure". Sunday and her gang were eventually slayed by Buffy Summers and her friends. Sunday was taken out by Buffy herself, who threw the handle of a tennis racket into her heart, killing her.
It is possible that Sunday was sired in the 80's, because her hairstyle and its cynical attitude evokes New Wave period (as Madonna, Cyndi Lauper, Annie Lennox...) as well as the characters of Bret Easton Ellis in his novel The Rules of Attraction. Also, the disappearances on campus weren't common until 1982.