What might a Southern woman in the mid-fifties wear that would make people around think she's Not Quite A Nice Girl? Not a hooker, just, like...forward? Bright lipstick, too much perfume, pants in public? She's a city woman, if that helps.
I just checked with my mom, who was in high school in the 50s -- she said her recollection, for both teens and grown-ups, was that there was, unsurprisingly, lots and lots and LOTS of conformity, and so there wouldn't be much visually to give you a clue. It was all pretty subtle. A sweater or skirt just a bit too tight. Hair not just dyed blonde, but bleached. For high school girls, chewing gum in class and smoking anywhere on school grounds. And attitude -- not appearing to seek everyone else's approval, or even care about it one way or the other.
But mostly, my mom said, because everyone looked and dressed so much alike, it was gossip. Fast women got smugly gossiped about by the guys who nailed them (or claimed to have), who let their friends and younger brothers in on it, who told their sisters and moms, who whispered behind their hands whenever She walked by, whether or not the guy who started it was telling anything resembling the truth.