10 year old daughter (middle child) is bright, athletic, does well in school and no behavior problems at school. Can be delightful, but extremely mean to younger sister (states because she annoys me) and has no tolerance for frustration...will get upset over small things and completely melt down. At times has said things such as "I wish I was dead" during the meltdowns. She is usually sent to room to calm down with mixed results. Worst is when this happens in the car and I cannot separate her from sisters (or myself) and she will not let up. Help!