Canfield's first credited performance on television was in March 1954 when she portrayed Frances in the episode "Native Dancer" on "Goodyear Playhouse". After making additional television appearances, she played housekeeper Amanda Allison on the sitcom "The Hathaways" during the 1961-1962 season. As Thelma Lou's "ugly" cousin in an episode of "The Andy Griffith Show", she had an arranged blind date with Gomer Pyle, played by Jim Nabors. Her name on this episode was her actual name, Mary Grace. The episode was originally scheduled to air on November 25, 1963, but it was preempted by the coverage of the assassination of President John F. Kennedy three days earlier.