What "good" comes from Liesel's nightmares

I think that Max and Liesel's nightmares reflect each others' and work as a sort of therapy for both. Abandonment is a key element of the lives of both Max and Liesel. They each have nightmares: one where Liesel is "abandoned" by her mother and brother, another where Max "abandons" his family. Neither of these episodes should be called true, deliberate abandonment, but both characters obviously feel guilty and deeply saddened by them. Max and Liesel share their emotional burdens with each other through the sharing of nightmares.