Meet the Austins — Madeleine L'engle

The moment Maggy Hamilton steps into the happy lives of the Austin family, she disrupts their harmonious world, bringing with her all the sullenness and insolence of her own misery.

Vicky Austin knows she should sympathize with Maggy for being an orphan, but she can't help but resent her for making life so difficult. It looks like Maggy may be a member of the family for a long time, possibly forever. Vicky remembers the happy times and finally accepts that things will never be the same, but she wonders what's to come.