Looking for Answers about Zonderkidz Carrying Mason?

Luna has learned a lot in her thirteen years-how to skin a rabbit, how to gut a fish, where to pick the perfect wildflowers-but it's not enough. When her best friend, Mason, dies, Luna leaves her large family and moves in with Mason's mentally disabled mother, Ruby Day. Caring for her takes a bit more learning and a lot more patience. Eventually they come to a backwards parenting relationship, working out the glitches and growing closer day by day as they help one another to grieve for Mason-until the arrival of a conniving aunt who wants Ruby Day locked away in a mental institution. How can a thriteen-year-old girl stand up to Ruby Day's aunt? What would Mason want her to do? And why is saying good-bye so difficult?