What's the purpose of the Ginnie Sue Pastor story?

Jeannette befriends a girl named Kathy Pastor whose mother, Ginnie Sue, works as a prostitute. When she visits, Jeannette intends to ask Ginnie Sue about her life as prostitute but she forgets and instead tells them about her life in California. All Jeanette learns is that prostitution puts food on the table. Jeannette actually encounters a person that is less well off and more marginalized than her own family situation. Jeannette is able to understand her friend's story without judgment.