Contrast Laura's attitude toward the workman with her attitude toward the silly boys of her social class. Why did she feel that way?
Laura's interest in the workingmen is triggered by the workman pinching off a sprig of lavender and smelling its fragrance. This simple gesture seemed to form a connection to her love of the beautiful. But at the same time she recognized the workmen as "real," beyond her experiences with the "silly boys" she knew. To her, they were "posers," interested in drawing attention to themselves,while the workman was interested in the simple things in life, just as Laura was. Or at least, as she imagined herself to be. When reality comes in the form of a death of one of the "simple" people in her neighborhood, she is overcome with horror, and soon retreats into her own "unreality" that is created by the people of her class.
With workmen, Laura isn't quite sure of her position, or who to be. When she sees them, she thinks "They looked impressive." She also "wished now that she had not got the bread-and-butter, but there was nowhere to put it, and she couldn't possibly throw it away. She blushed and tried to look severe and even a little bit short-sighted as she came up to them." In other words, she has to pretend to be someone she thinks she's supposed to be with them. Once they reassure her, she thinks how nice they are. Finally, she feels moved to speak with them. By contrast, with boys of her class, she feels less unbalanced, but also less moved to emotional/true speech.