I imagine she was wearing a drysuit, and I'm pretty sure I read that she was using a twinset. That would have been steel, in England. She would have needed a great deal of weight just to be able to descend - typically I wear 12-14 kilos when diving off the English south coast. She might not have been able to ditch weight, or (as is very common) might have been reluctant to lose it. I obviously don't know any more that anyone else what actually happened, but if I were investigating I'd want to look at the normal procedures on that boat for recovering divers. Having difficulty approaching a boat in those conditions is normal, and many years ago my regular boats introduced long floating lines with several attachment points, so gear could be (first) attached to a line and then removed from the body, so the boat could be approached without the inertia of heavy gear. Later the whole process became easier and safer when hoists were introduced.