Foster has worked extensively in the theatre since studying with Sanford Meisner at the Neighborhood Playhouse in New York. Her stage credits include "King Lear", "Barabbas", "Three Sisters" and "Extremities", among others.
Had a relationship with Ron Starr, they had a son named Christopher Starr. She and son Christopher starred together in The Osterman Weekend (1983) directed by Sam Peckinpah, who directed Ron in Ride the High Country (1962).
She was replaced with Sharon Gless on Cagney & Lacey (1981) after 6 episodes. CBS reportedly wanted somebody more "feminine".