I haven't read through 70 pages of this. I feel very sorry for what happened to this teenager. Wrong decisions all over the place, one after another. I normally don't have an opinion on responsibility, but in this case the avalange of mistakes made is just overwhelming.
The only thing I can comment on is the effect of squeeze. Not in the context of a drysuit workshop, because I don't teach these. I find that a couple of 1 on 1 mentoring dives with some theory are enough to show them the ropes. However I do use this picture as a case of making bad decisions and task overloading, in my tech or essentials courses, mainly to show them to stop and fix before continuing.
This is my chest and the impression of a VW passat car key pressed into it due to drysuit squeeze. I don't have pictures of my arms and back full of blue, black bruises, but there were alot. The key was on a leash not on my bare skin, there was a t-shirt inbetween, and then my undersuit. It happened during a north sea dive in 2013, with a lot of current and waves topside and a lot of confusion between diveteams on the charter. So equipment (GUE EDGE) check was minimal (first mistake), and we dropped in and descended. There was a lot of current, which ment we needed to pull on the buoy line to the wreck. At about 20ft I noticed the squeeze and realised that my drysuit hose was not connected. I made the decision not to signal my buddy (who was pulling himself down below me) and decided to fix it when we would reach the wreck (at 130ft). In the end I did stop and fixed it (connecting the hose) after stopping at 100ft and signalling my buddy to wait. Reason being that the squeeze became unmanageable.
This was me, an experienced diver, with at that time at least 800 drysuit dives under my belt, hogarthian setup, not being overweighted. The squeeze almost overwhelmed me, and I'm reasonably sure that if I had sank another 30 ft that it would have become hard even to just reach my wing inflator, so rigid was the suit. This imprint on my skin happened after only a couple of min, and I wore it for a week.
So imagine an 18 y girl, with 5 dives under her belt, dropped in a cold, bad vis enviroment, using equipment (a drysuit) she never used before, overweighted to the hilt, with an absent instructor (herself not experienced?, task overloaded?, focused on the other students or the task in her mind?). She had no chance :-( I feel so sorry for this young girl and her family.
PS: this is the key btw.