The Smallest Cow in the World: A Heartwarming Story About Best Friends and New Beginnings for Kids (Ages 4-8) (I Can Read Level 3) by Katherine Paterson

Moving is not easy. Rosie is the meanest cow in the world -- and Marvin's best friend. When his family moves to a new farm, Marvin is sad and lonely . . . until he finds Rosie again. But now she's making a lot of trouble for everyone. Will she and Marvin ever adjust to the changes of a new life in a new place?