Rupp's list of stage credits includes appearances in Terrence McNally's "Frankie and Johnny in the Clair de Lune" and Cynthia Heimel's "A Girl's Guide to Chaos", the Broadway role which propelled her career forward. She originated the role of Cynthia in 1986, a character based on Heimel's observations made during her stints as a columnist for "Playboy" and "The Village Voice". Directed by Wynn Handman and sharing the stage with Rita Jenrette, Rupp's performance as Cynthia was immortalized by legendary caricaturist Al Hirschfeld and described in a "New York Times" review as "an appealing mixture of pluck and pathos." In his review of "Chaos", "New York Newsday" theater critic Allan Wallach called Rupp “a real find.”