Green’s Dictionary of Slang

(US teen) a female member of a street gang.

1944		Des Moines Register (IA) 13 Aug. 2/2: The deb-gangs mostly consist of six to 15 members [...] there is a low percentage of venereal infection or illegitimate births among the debs .
1950		Hal Ellson Tomboy (1952) 10: Why isn’t she like the rest of the debs in the gang.
1959		E. De Roo Go, Man, Go! 42: All the gang and their debs were talking about the big bet.
1964		‘Charles Barrett’ Address: Kings Cross 16: She’d been a deb two years before and had been to parties at our house.
1964		Larner & Tefferteller Addict in the Street (1966) 123: We were Black Diamond Debs.
1967		P. Thomas Down These Mean Streets (1970) 18: All our movie money. And all the change we could beat out of our girl-debs.
1977		(con. 1960s) D. Goines Black Gangster (1991) 28: One of the debs in your gang is screwing everybody.
1994		P. Baker Blood Posse 15: Sisters, you ain’t forgotten neither, we need Debs.
1999		Indep. The Information 16–22 Oct. 35: A disparate group of high-school students – a jock, a goth, a deb, and a nerd.