Why does Laurie seem upset at the end of chapter 3?

Laurie is still disturbed by the movie—so much that she has lost her appetite. She gives her hamburger to David, whose appetite is fine. Amy and Brian Ammon join them at their table. Brian complains that the football team will probably lose its game this weekend. The players are disorganized and many do not show up to practice. Laurie is still upset about the movie, but David believes that she is taking it too seriously.