Disappointed at never being given a strong movie part, she quit films in 1943 and moved to radio, TV and stage work.
Her ex-husband, Henry Jaffe, was a New York City attorney.
Her name appeared in "Red Channels" the "anti-Communist" pamphlet and her career was irreparably damaged. This led to a bout with alcoholism, which she recovered from.
In 1950 she was blacklisted by the television industry as a suspected Communist.
In later years she taught drama in community playhouses and summer drama schools.
In the 30s as a Warner Bros.' contract player, she was nicknamed "The Studio Pest" because she always had questions about everything from camera angles to publicity practices.
Was the original choice for Errol Flynn's leading lady in the classic swashbuckler Captain Blood (1935) but the role ultimately went to young 18-year-old Olivia de Havilland, who impressed critics and audiences in the film A Midsummer Night's Dream (1935), which also co-starred Ms. Muir.