Mitchell was believed to be the last surviving adult castmember from the legendary CBS sitcom. She died on November 11 of heart failure at her condominium in Westwood, her sister-in-law, the Oscar-nominated Sunset Blvd actress Nancy Olson, told The Hollywood Reporter.
The actress joined the show for the 1953-54 season and appeared in three episodes.
Mitchell also starred in 'Bachelor Father', 'Please Don't Eat the Daisies', 'Petticoat Junction' and 'The Beverly Hillbillies'.
She also appeared in films like 'Jamboree', 'Desk Set', 'Big Business' and 'The War of the Roses'.