Ginny Morris and Dads New Girlfriend — Mary Collins Gallagher

Ten-year-old Ginny Morris, whose parents are divorced, lives with each parent a week at a time. One day when she arrives at her dad's after a week with her mother, she discovers that the house is spotless, the yard is spruced up, and even her own room has been messed with. The reason is: Dad has a friend named Ruth.