Thanks for the further info Amtrosie.
Not having done the Rescue course (as yet), I wouldn't know the first steps in dealing with a panicked diver - for their safety as well as my own.
It seems from this latest news that she was still at the surface. Maybe there was something else that panicked her - i noticed they haven't got the results of the toxicology report as yet and as you so rightly put it, "none of us who were not there will ever know."
The only lessons that we can learn from this is to make sure that if we are uncomfortable about diving due to anything (equipment, our own state of mind, feeling uncomfortable about the conditions or have a sixth-sense about something), we should a.) speak to someone or b.)abort the dive altogether (you may say thats a bit drastic).
If it's someone else - either our buddy or someone we have never met before - we should have the balls to say something and make sure that they are comfortable about doing the dive....it might save a situation similar to this happening.