I'm sure this is the work of bearded vultures rather than griffons. They drop bones from a height onto rocks in particular spots like the scree beneath P de la G in order to break them. They then eat the bones (the actual bones, not just the marrow). The implication is that not only were the bones carried there from, well, almost anywhere (except from under forest cover), but the vultures have probably been smashing and eating the bones for some time, given the apparent state of the pieces found. I'm sure that griffons also got to the body elsewhere. IMO, the presence of the bones beneath P de la Glere doesn't mean that Esther went anywhere near the place herself. I tend to think the whole P de la Glere thing is a false lead in terms of knowing how/where she met her fate.