The answer is "Her parents have forced her to move."
This is shown in the quote from the text, "Her parents had moved her to Cincinnati... difficult... suffering (Rylant paragraphs 1 and 2).
This uncovers the idea that the girl had not chosen to move- her parents had not given her an option. In effect of moving, the girl is "suffering" and it is "difficult" for her. Clearly, this exhibits her sadness and mental pain.
