Complex sentence: The diary claims that Isabella is a shy, quiet girl who had a romantic and intimate relationship with Chris over the summer and together they discover from Isabella's Aunt, a psychic, that one of them would die in the woods.
Split into simpler sentences: The diary claims that Isabella is a shy, quiet girl who had a romantic and intimate relationship with Chris over the summer. They also discover in the diary that Isabella and Chris went to a psychic and learned that one of them would die in the woods.