Allman made her film debut as an actress in 1940s Road to Singapore in an unbilled bit as a homely woman pursuing Bob Hope. The role was an unbilled bit like the majority of Allman's motion picture appearances in the 1940s. She worked most successfully during this period as a radio comedienne playing assorted guest parts, typically as a shrewish woman. One of her more steady radio gigs was on the Blondie radio series in the part of "Cora Dithers", the domineering wife of Dagwood Bumstead's boss.
Allman became a familiar face to television viewers in the 1950s with numerous guest appearances on many programs of the era, usually situation comedies. She made multiple appearances on I Married Joan, December Bride, Love That Bob, and The Abbott and Costello Show, and three appearances on I Love Lucy, most notably as the stern candy factory boss who thinks that Lucy and Ethel are fast because they have hidden (and eaten) the unwrapped candy from the conveyor belt, says, "Fine, you're doing splendidly," and then turns and shouts off-camera, "Speed it up a little!"
In 1957, she reprised her role of "Cora Dithers" in a short-lived TV adaption of Blondie (1957 TV series). She also appeared on seven episodes of the series The Jack Benny Show, having worked often with Benny on his radio program in the 1940s and 1950s.
Her visibility on television increased in the 1960s with guest shots on The Dick Van Dyke Show, Hazel (TV series), The Addams Family (TV series), The Munsters, Bewitched, The Lucy Show,The Doris Day Show,and The Andy Griffith Show. Allman's greatest fame came with her semi-regular roles on Petticoat Junction, as local busybody "Selma Plout" (14 appearances, 1965–1970) and a near-duplicate character, "Elverna Bradshaw" on The Beverly Hillbillies (13 appearances, one in 1963, the rest 1968-1970). The 1960s proved to be her most prolific era with 58 appearances on various television series as well as five motion pictures including Breakfast at Tiffany's and The Nutty Professor.
She appeared as Oscar Madison's mother in one episode of the TV series The Odd Couple (she and Oscar are treated to an erotic belly dance at a Greek restaurant). Allman's career slowed down considerably after 1972 and her only television work in the late-1970s was in an Addams Family television movie. Her career revived a bit in the 1980s with eleven television appearances including two appearances on Murder She Wrote. Allman also worked as a real estate agent in addition to her acting in the 1970s and 1980s. In her autobiography, Mary Tyler Moore credits Allman with finding her house.
Allman's final work appropriately brought her full circle, reviving the voice of Clarabelle Cow for the first time in over 50 years in the Mickey Mouse cartoon feature version of The Prince and the Pauper in 1990. She died two years later from pneumonia, aged 87. She was predeceased by her last husband, Jerome L. Bayler, in 1978.