At the end of the book, Wendy goes back to New York City to be with Josh and Louie. As she picks Louie up from school, she reflects on how they'll have to have a memorial service for her mother soon and how sad that will be:
They would be very sad that day, and for many days after. In certain ways always. They would also never be the same as how they used to be. But they would also be happy. (34.120)
Wendy recognizes that in saying goodbye to Janet—and accepting that she is not coming back again—they can move on as a family. They'll have the freedom to be happy again, and that's the optimistic note the story ends on. Even in the face of such tragedy, there is light and joy at the end. We have a hunch Janet would approve.