With all due respect, do you really think being an instructor, even at the highest levels, makes one immune from DCS? If so, then you are very naive, no offence meant. Just like Dr's, instructors are not God (although some, and I repeat only 'some', think they are).
And depending of the severity of the hit, the term 'close' (as in chamber) is a very broad term with regards treatment response time.
That being said, I do not know the deceased person and cast no aspirations on her, as matter of fact I send heartfelt condolences to her family and friends, as I too have lost close friends myself in the underwater world we visit.