The birches on your photo are small, they grow on the upper tree line and in these conditions they rarely reach more than 5m in height. Their trunks are narrow, and would hardly cause much damage. Also, as they don't have leaves in winter, strong wind or a blast wave would probably not break them, as there is not enough mass for that. That's why I said that if a tree would fall on them, it would probably be a coniferous tree, as they grow larger in that area and break more easily in wind.
Regarding photo of Zina, yes, that could have been bark and needles, but only on a limited body surface, most probably from sitting on a log of dragging cut branches. I am not sure if you have ever seen a coniferous tree fall. The needles would be everywhere, and I really mean it.
I am sorry, but my mind is open here. I don't exclude possibilities, just trying to find some direct hard evidence. I wanted to be polite, but I think it is you who is married to a theory. I am just trying to tell that there is no direct evidence that it was all caused by a tree. There is no evidence that the tent was even moved. There is no evidence that there was any cleanup. It is all just speculations. Anything could have happened, if it fits into your theory. But in case you find new evidence for your theory in the pass, I will happily let myself to be convinced..