I was a victim of childhood sexual abuse and prolonged mental abuse. These are my opinons on what could be going on.

To me it sounds like the story about albert is a revenge phantasy to get back at her parents. I'd suggest speaking to a clinical psychologist who's a specialist in trauma for their advice.

I suspect the letter was written by Edie and left for the police to find as evidence of what happened to her and reasoning as to why she is gone. It's clear that she felt very let down by cps and her school teachers and i think that she probably either ran away or committed suicide. As sad as the latter is, its statistically likely.

Have you made an appeal for her through the media?

EDIT: I have serious mental health problems and used to see myself as third person while having flashbacks about the abuse. Its possible that Edie was writing in third person based on this.