snipped for focus
You have echoed what I have thought could be significant for a while, and I think I may have posted on it upthread somewhere.
The gap between the postings on 21st (photos taken around midday judging by the shadows, and posted to IG from the summit at the time I suspect, based on the wording in the present tense "maybe I can see you" and the fact she was right next to a mast) and then the sighting by Vigo which is over 24 hours later. Nothing in between, this seems out of character, and inconsistent with her posting patterns. According to Dan signal was generally very good in the area, though missing in some areas.