Answer: It demonstrates that Nora is considering leaving her children.
When Nora talks to the nurse, we get an indication of Nora's future plans. We know that she does not feel satisfied with her life, and that she is not a maternal person. Nora feels trapped by the traditional role she has to play. When she talks to the nurse, she expresses her concern with the fate of her children. She wonders what would happen to them if she left, and is comforted knowing that the children are likely to be fine.