Sowle is most notable for her role of Mrs. Bucket (Charlie Bucket's mother) in the 1971 film Willy Wonka & the Chocolate Factory, and her performance of the song "Cheer Up Charlie" (although dubbed by Diana Lee)in that film. Following the death of Leonard Stone in 2011 (who played Mr. Sam Beauregarde in the film), she is the last surviving parent of a child character in the film. Following the death of Gene Wilder in 2016, she became one of few living adult cast members, the others being as Tim Brooke-Taylor who played the computer scientist, Gloria Manon who played Mrs. Curtis, and three Oompa-Loompas, including Rusty Goffe.

Her only other screen roles to date came in 1994 when she appeared in Clear and Present Danger and Guarding Tess.

Sowle also does the voice acting for the character Agatha in the game Fallout 3, released in 2008.

In the summer of 2012 she appeared in a production of Love Letters with F-Troop star Larry Storch in Farmville, VA to benefit The Tom Mix Rangers.

Sowle is a native of California and lived in the Washington, D.C., area, where her husband worked for the CIA. He died in 2013.