Jessica, Paperback

"There is no Jessica," said Ruthie's parents. But of course there was. She ate with Ruthie, played with Ruthie, and was sorry when Ruthie was bad. Nobody could see Jessica -- except Ruthie. When it came time for Ruthie to go to school, Jessica went with her. Her parents hoped Ruthie would find a friend at school who would replace Jessica. They were in for a (happy) surprise