What happens at the end of the conversation with Mrs. Brook?

In Chapter Three, Caitlin is baffled and uncomfortable in her sessions with Mrs. Brook. She grows to hate the psychologist's opening line: "Let's talk about it." When Mrs. Brook quizzes Caitlin about how she felt at her brother's funeral, Caitlin repeatedly answers her questions with "I don't know." Finally she asks the psychologist to stop asking her questions. Mrs. Brook tells Caitlin that her father is sad because he misses Devon; she assures Caitlin that her brother is still with her but in a different way. Caitlin angrily protests that she wants her brother around in the old way "when he makes me popcorn and hot chocolate" instead of the new way. While visiting Mrs. Brook one afternoon, Caitlin climbs under the table to escape her eyes and rubs her finger on the raw wood until it bleeds, then continues rubbing and smears blood everywhere. She persists although Mrs. Brook tells her to stop.