Her first film was 1932's Age of Consent, in which she co-lead. She made 21 films during her Hollywood career. She would retire after marrying Oscar-winning scriptwriter Lewis R. Foster (His Oscar was for writing Mr. Smith Goes to Washington - Fantastic film by the way).
She replaced Ida Lupino in 1935's The Milky Way
She was asked to test for the role of Melanie in 1939's Gone With the Wind. We all know the part went to Olivia de Havilland, but it would be interesting to see how Dorothy would have done. She is quoted as saying that was the only role that could have brought her out of retirement. I wonder what sort of career we missed out on because she lost the role . . .