The Pretty Girl 21 years old

In a reverie, a young woman (the pretty girl) puzzles out why no one is smiling at her the way they did, except for some women, and those smiles seem different. A male voice narrates. She thinks back to Saturday night. She wore her red dress, a dress smaller than a dress anyone else in town can wear. She went out dancing; she danced and drank and smoke and flirted. She was the last to leave, walking home alone, as usual, by way of the beach. That's the nicest part of the evening, and the nicest part of the nicest part is removing the dress, swimming, and putting the dress on again while still dripping wet. She walks the rest of the way home. What changes things?