Becoming a child Actress at the age of ten, Haddock is perhaps best known for her role as tomboy "Cindy Webster" on the first season of the NBC television series The Facts of Life. She is also known for her appearance on the Wonder Woman television series as the super powered girl, Amadonna, in the episode The Girl from Islandia and as Robert Duvall's daughter in the movie The Great Santini. She also appeared as Melinda Mulligan, the daughter of Lawrence Pressman and Elinor Donahue on the short-lived NBC series, Mulligan's Stew, in 1977. In the 1983-1984 season, she appeared on NBC's short-lived Boone starring Tom Byrd and Barry Corbin.
In 2008, Haddock, along with Molly Ringwald, Felice Schachter, and Julie Piekarski, was nominated for a TV Land Award, in the category Favorite Characters Who "Went Missing"
