What is the meaning of the given line "Sophiewatched her back stooped over the sink and wondered at the incongruity of the delicate bow which fastened her apron strings. The delicate-seeming bow and the crooked back. The evening had already blacked in the windows and the small room was steamy from the the stove and cluttered with the heavy- breathing man in his vest at the table and the dirty washing piled up in the corner."

Please Describe the meaning .