Daughter of Frenchborn Robert PerreauSaussine and Eleanor Child PerreauSaussine she was born Ghislaine Elizabeth Marie Thérèse PerreauSaussine Perreau achieved success as a child actress in a number of films She got into the business quite by accident Her older brother Gerald was trying out for the part of the title characters son in Madame Curie Because their mother could not find a babysitter she took Gigi along The twoyearold who could speak French got the uncredited part of Madame Curies daughter Ève while Gerald would have to wait a year to make his film debut in Passage to Marseille She also played the daughter of Claude Rains and Bette Daviss characters in the 1944 film Mr Skeffington In Shadow on the Wall she starred as the sole witness to a murder As the top child movie actress for 1951 the then tenyearold was given the keys to the city of Pittsburgh by its mayor and later Pennsylvania governor David L Lawrence She was the youngest person to be so honored Perreau played the rebellious teen daughter of Fredric March in 1956s The Man in the Gray Flannel Suit However her film career lost momentum as she became an adult so she turned to television In 1959 she played a friend of Shelley Fabares on The Donna Reed Show and had a supporting role in the sitcom The Betty Hutton Show with her brother Gerald In 1960 Perreau and Robert Harland performed as Sara Lou and Lin Proctor a young couple from the east who have eloped and are heading west in the western series Stagecoach West with Wayne Rogers and Robert Bray Also in 1960 Perreau was cast as Julie Staunton in an episode of The Islanders set in the South Pacific She was cast in Don Gringo and The Promise as well as in The Rebel In 1961 she played Mary Bettelheim in an episode of The Roaring 20s She was cast in a recurring role on Follow the Sun series from 19611962 as secretary Katherine Ann Kathy Richards She guest starred on The Rifleman in 1960 and 1961 She made guest appearances on Perry Mason In 1964 she also costarred as Lucy a beleaguered homesteader on an episode of Gunsmoke In 1970 she appeared on The Brady Bunch as a math teacher who becomes the object of puppy love by Greg Brady one of her students In the 2000s she provided her voice in the animated films Fly Me to the Moon A Turtles Tale Sammys Adventures and Crash The Animated Movie and acted in Time Again