She was born Caecilia Lvovsky. Her father was a minor Czech classical composer. She studied at the Royal Academy and went on to appear in stage plays in Austria and Germany until meeting Peter Lorre, whom she later married. She was instrumental in getting him cast as the child murderer in Fritz Lang's M. Although the couple divorced in 1945, they remained devoted friends all their lives. Lorre would not permit her to work in America, believing that in a marriage the man must do all the work. After the divorce she sought out theater and film roles, but was hampered by a heavy Austro-Hungarian accent. She did get a number of character and exotic roles. She played Lon Chaney's deaf-mute mom in Man of a Thousand Faces where she used American Sign Language most gracefully. Late-night viewers probably remember her in this role or as Apache Princess Saba in an obscure 1955 film, Foxfire, directed by Joseph Pevney. It is possible that Pevney suggested casting her as T'Pau based on his prior work with her.
For more on the subject, see The Indian-Star Trek Connection.