Who is The Three Dressmakers from A Walker in the City and what is their importance?

In Part 2 ("The Kitchen"), the author writes at considerable length and in considerable detail about the regular Friday night conversations around the kitchen table between his parents (particularly his mother) and three women dressmakers. One was a cousin who roomed with the family, the other two were her friends. The author's descriptions of the women and their conversations are tinged with sexual longing (as he describes the way their blouses fall across their breasts), intellectual respect (as he describes their passion for, and knowledge of, socialism) and longing.