The Story of Molly X (1949)

Molly's husband Rick was a gang leader in Kansas City. After he's shot, the tough woman moves to San Francisco with a couple of the gang to start anew. Disguised as a rich woman, she and her gang rob security transports. But when one day Rod confesses to her that he killed Rick out of jealousy, she shoots him down immediately. In lack of proof she can't be convicted for the murder, but she goes to jail for the robberies. It's a new and very open female prison, where she learns a profession for the first time in her life.