What happened when David came to visit Knapp after college?

David had moved to Chicago a little while before, and when he came to visit Knapp, he was supposed to stay for the summer. When he decided to go to Europe for the summer, Knapp was furious, but instead of voicing the anger and pain, she told herself she would not eat. This continued on. She could control the food, but not what was happening around her. Knapp also began to work out obsessively.