The Dreadful Wolf Girl

(from ebookjapan):
It was a harsh Scandinavian winter, when Christy was 7 years old and Leena was 6. Leena, who was selfish, whiny, and whiny, was always told by her parents that she should be eaten by wolves by now. Leena is left outside the house in the middle of winter, and is attacked by a wolf, never to walk again. For the next seven years, Christy cared for Leena and enjoyed her youth as much as anyone else. However, her long life as a caregiver has twisted Leena's mind completely...