I have been to Everest Base Camp and to the top of Kilimanjaro, so a bit short of 6,000 metres and I know the feeling of altitude. I know my limits, and I can't imagine climbing another 3,000 metres. On the Everest trek, the fittest member of the group was playing volleyball with the locals at around 4,200 metres. However, when we got to about 4,800 metres, where we were camping on the way up, he started vomiting overnight and had to be sent back down. AMS is an odd thing. You can never predict who it will hit worst, even the most aerobic fit people can suffer. On the Kilimanjaro trek, a German in a different group died in the campsite where we had stopped for the night.

Read his book it’s well written

She did the correct thing

Interesting. She was a track sprinter. Cycling reveals physiologies. Eg grand tours that go over 3,000 metres select certain riders while others, who might be stronger in other environments go backwards, eg Alexandro Valverde. Her dense heavy natural muscle would not be suited to high altitude