Bone by Bone by Kay Sanjida

Laura loves her daughter more than anything in the world. But nine-year-old Autumn is being bullied. Laura feels helpless. When Autumn fails to return home from school one day, Laura goes looking for her. She finds a crowd of older children taunting her little girl. In the heat of the moment, Laura makes a terrible choice. A choice that will have devastating consequences for her and her daughter.