
Mallory was known for her work in the theater and on television. On TV, she starred as pianist Leslie Brooks on the CBS daytime soap opera The Young and the Restless from 1977 to 1982, visiting again in 1984. Later, she played Dr. Denise Foxworthy on NBC's Santa Barbara. Her other television credits included guest starring roles on Everwood, Touched By An Angel, Promised Land, the female lead in the made-for-television movie Unabomber: The True Story, and three CBS musical specials, The Emperor's New Clothes, Aladdin, and After Hours: Singin', Swingin' and All That Jazz, which won an Emmy Award in 1978 for Outstanding Individual Achievement in Daytime Programming.
Mallory made her Broadway debut when Richard Rodgers chose her to star as Maria in the first revival of "West Side Story" at Lincoln Center. She then went on to play Lili in City Center's revival of "Carnival." Mallory originated the role of Young Heidi in the Harold Prince/Stephen Sondheim production of "Follies" as well as the starring role of Anne Egerman in "A Little Night Music."