Moll

(plural molls)

• A female companion of a gangster, especially a former or current prostitute.

Citations: 1920, Mary Roberts Rinehart; Avery Hopwood, chapter I, in The Bat: A Novel from the Play (Dell Book; 241), New York, N.Y.: Dell Publishing Company, OCLC 20230794, page 01:

"The Bat—they called him the Bat. […]. He […] played a lone hand, […]. Most lone wolves had a moll at any rate—women were their ruin—but if the Bat had a moll, not even the grapevine telegraph could locate her."