"Ginger girl has two meanings (outside of the urban east) that I know from childhood; a redhead or ginger-headed (hair sort of a reddish-brown, face often freckled). Ginger girls are what we called the girls who built up school spirit in pep rallies, etc."

Thanks, Q for that information. I'm wondering if these two meanings might be connected in that folks may have believed that a redheaded girl had more energy {temper?} than girls who have other colored hair [naturally and not dyed hair color, that is]and that's why girls who built up school spirit at pep rallies {cheer leaders?] were called "ginger girls".