How in the story does the first-person narration enlist and direct our sympathy?

Mrs. Johnson narrates the story in the first-person. As a result, we are exposed to her personal feelings and emotions. Dee's treatment of both her mother and sister are all the more personal because they are seen through the eyes of her mother. We realize that she loves both of her girls, but that she is fiercely protective of the youngest. We also see her feelings about the way Dee turned her back on her family because they weren't enough..... at least until returning served her own purposes.

(because they weren't enough..... at least until returning served her own purposes.)what is that means?