What rules and conventions are customers expected to follow in a supermarket? How does the behavior of Queenie and her friends violate these rules?

The customers are expected to be relatively quiet and move in the direction of the isle traffic flow. Customers are not expected to be happy or excited. Their manner should reflect their drab middle class lives. The girls, by contrast, are vivacious and happy. They exude sexuality, to Sam anyway, and break the noise codes of the store. They walk against the flow of isle traffic and flitter around instead of following a mapped out routine.