I'm writing a suspense/horror story dealing with witchcraft and the supernatural. I have this mentally unstable supporting character (Cheryl Davis is what I named her) who has just recently checked out of a clinic and is newly rehabilitated. One night, the main character invites Cheryl and her family to the mansion, and they end up staying there overnight with her family. Throughout the evening, the mansion's energy causes Cheryl to gradually break down (with hallucinations and mysterious voices coming from the ceiling) until the point where she finally delves into complete insanity. How should I approach this? I'm not sure exactly how I'm going to handle the character. Should I have her suffer weird dreams or hallucinations before she and her family go to the mansion, as kind of like an early warning sign of whats to come? Any advice would be great.