In 1946, at age 15 she gave birth to her daughter Judith but did not marry the father, described as a "Navy man" stationed in Long Beach, California.

Changing her last name to "Castle", she modeled for a swimwear company and caught the attention of a Columbia Pictures talent scout who noticed the 5'6" brunette bore a striking resemblance to Rita Hayworth and subsequently signed her as an actress.

[2] Columbia immediately set about exploiting the story by including her in a number of 1950 films: The Tougher They Come, Prairie Roundup, and Texans Never Cry.

[3] In the opening of The Tougher They Come, Castle was shown sitting at a bar, "blankly staring ahead, her resemblance to Hayworth startling [and] her line readings deliberately slow and sultry to mimic her famous counterpart.

Upon Hayworth's return to Hollywood, following her separation from Aly Khan, Castle's contract with Columbia was allowed to expire on March 7, 1951.

'"[3] Working for Universal Pictures, Castle continued to star in westerns, often playing a tough, physical role, such as the saloon singer Cora Dufrayne in the film version of Gunsmoke.

[4][5] A weekly 30 minute show, Castle proved to be a capable action figure, both with guns and her fists, engaging in catfights with Marie Windsor as "Belle Starr" and Joan Shawlee, an outlaw moll in "The Doolin Gang".

Castle battled male actors as well, pistol-whipping Bruce Bennett ("Quantrill and His Raiders") and Slim Pickens ("The Wild Bunch of Wyoming").

[6] Despite Stories of the Century winning an Emmy for Best Western or Adventure Series, Castle was replaced by Kristine Miller.

Although reason for the change was never made public,[2] Miller said that she had been the original choice for the series but declined because she was pregnant, telling a journalist "So Mary did the first ones.

In 1957 Republic Pictures released The Last Stagecoach West, co-starring Castle and Davis, that was originally filmed as the pilot for Stories of the Century earlier in the decade.

[3] On Christmas Eve, 1957, Castle and her then husband, William France Minchen engaged in a physical fight, blocking Sunset Strip traffic.

Less than a week after her release, she pleaded guilty to failing to appear in court on a 1958 traffic violation, running a red light and not having her license, and was ordered to pay a $50 fine.