I don't have all the information and I am not a medical professional, but what I was told is that the hiker started losing her eyesight near the summit and after summiting her eyesight got worse and worse until she could no longer follow the trail and got lost in the boulder field (with possible "Window" dropoffs!) on the Mount Whitney Ridge. I also heard: "The Hospital staff told her she only had hours to live had we not found her and stabilized her at Trail Camp." So those hero hikers that got her down from the Mount Whitney High Altitude "Death Zone" Ridge really saved her life. She was coughing pretty bad so I assume HAPE in addition to HACE.