she could have tried to get help; he could have told her to try to go down; the top is rocky and either of them could have tripped. once the weather is bad, down means: less wind, less precipitation, less windchill, but you could totally lose visibility - some of the trail markers are cairns or white marks on the rocks... it could fog up and you would only be able to see a short distance. not sure if they had a navigation device. also not sure if they had down coats or a sleeping bag. I had a few spots where in perfect weather, I was looking carefully for a place to put my foot to keep safe. and you get tired.Why would she go away from the trail and be far from her dad ? I fail to see what could have happened to her father first, an then her. was the weather still that unstable and cold ?
Did he have a health issue eg stroke due to the difficulty of the hike and did she leave to get help?