In her 20s, she moved to New York City and appeared in a number of Broadway shows, catching the eye of choreographer Bob Fosse who cast her as a replacement dancer in Pippin. She had a secondary lead in the stage version of the film Gigi in 1973, and later appeared in Mack & Mabel, and as Judy in the renowned "new New York cast" of A Chorus Line (when many of the original actors left the show in 1977). She was cast again by Fosse in his critically acclaimed 1978 dance concert/musical Dancin', which featured many of the top dancers on Broadway at the time.
Bergman's movie career began in 1978 with a small role in the TV film How to Pick Up Girls. She followed this in 1979 with a noted appearance as a dancer in the Fosse film All That Jazz, in which she was a featured performer in the "Air-otica" sequence. In the 1980 movie Xanadu, she appears as one of the nine immortal Muses during the opening song "I'm Alive" by ELO as well as the final title number of Xanadu.
Bergman's participation in Xanadu also led indirectly to her eviction from her apartment in New York and her subsequent relocation to California. She had been subletting her apartment in New York in defiance of a clause in her agreement with her landlord, and during her four months in California for filming, he became aware of the situation. Bergman has said she never returned to New York, instead having friends pack and ship her clothes to her. Her best-known role was playing "Valeria" opposite Arnold Schwarzenegger in the 1982 film Conan the Barbarian. She won the Golden Globe Award for New Star of the Year - Actress for her role in the film. Because no stunt women could be found to match her size, she learned to do all her own stunt work. She commented on the experience, "It was tough. I nearly lost a finger. Arnold smashed his head against a rock. But that was nothing compared to what the stunt men went through."