Final answer:
The author describes the flower girl's clean apron and tidied coat to show her attempt to appear presentable, reflecting her lower-class status and personal dignity.
Step-by-step explanation:
The author’s description of the flower girl's attire serves to highlight the effort she has made to present herself neatly despite her lower-class background. This detail characterizes the flower girl and enhances our understanding of her social position and personal dignity. It is not merely for the benefit of the costume designer or to show poor taste in clothing, but to provide depth to the character and her circumstances.