I didn't have a kill list.
Instead I put a visual story on my Design Technology portfolio.
It was of a boy who was badly bullied at school, because he had a big head the shape of a brain. He proceeded to get revenge by stabbing one child and trapping one child in a barbed wire net, letting them fall through it in chunks, whilst the rest of them were covered in acid from a giant pot that hung above the assembly hall. He died in the end, after having a chainsaw/pipe fight with someone, whereas sparks shot into his eyes, and he fell off the end of the school roof.
I had problems, was extremely shy to the point of avoiding others until around the start of Year 8 (I drew it in Year 7) and whilst I did hang around friends, I was tormented both at school and at home, until I left high school and the mainland. I loved animals though. Some teachers were nice, but I wish that my mental health had been zoned in on more whilst I was at school, especially as my grades were good prior and I didn't have these stories in my head before high school. I did have red flags.
My opinion? The person who wrote the kill list needs to be both heavily monitored and investigated, but also emotionally supported. Your daughter didn't deserve this (even if she was a bully, which has been refuted in this thread), but her life and her studies shouldn't be disrupted by it.