After 164 posts, I am going to try to list what is known about this case, replying primarily on the several people who posted eyewitness accounts. Please correct any misinformation.
1. The victim was a very experienced diver with many dives around the world.
2. The victim was using a mixture of personal and rental equipment, and there was a mismatch with the inflator hose system. [Speculation: her BCD was equipped with an inline alternate air source, but the rental BCD included a conventional inflator hose. You cannot use a conventional inflator hose with an inline alternate air source.]
3. The victim agreed to use the system for the dive, using oral inflation to achieve buoyancy.
4. During the dive, the victim indicated she was not feeling well and wished to end the dive.
5. The DM accompanied her for part of the ascent, but she had no assigned buddy for the ascent, and no one saw her reach the surface.
6. She was later found deceased on the reef by another couple.
7. The couple that found her later heard that she had suffered a stroke.