Other forms: molls
A woman who's the companion or conspirator to a gangster can be called a moll. One of the most famous molls was Bonnie Parker, of the criminal duo Bonnie and Clyde.
The informal moll has most often been used for the romantic partners of 1920s and 30s mobsters, like Al Capone's wife Mae or George "Baby Face" Nelson's girlfriend Helen. These supportive women were also called "gun molls," not named after the weapon, but for gonif, the Yiddish word for "thief." Moll is a shortened form of the name Molly, long a synonym for "woman of ill repute," for unknown reasons.