Green’s Dictionary of Slang

a derog. term for a white woman; thus by ext. a black woman who apes her white sisters.

1971		(con. 1930s–50s) D. Wells Night People 117: Ann. White girl.
1972		J. Maryland ‘Shoe-shine on 63rd’ in Kochman Rappin’ and Stylin’ Out 212: Who said anything about Sweet Blood [...] running around here with Ann?
1989		H. Rawson Dict. of Invective (1991) 279: Other generics include: [...] Ann, a white woman.