If Esther arrived at the Refuge de Venasque, she should have left evidence that she was there. She was required to sign the attendance book and make a payment. Since there is no evidence that she was at the refuge, I think she must have had an accident between the Pic de Sauvegarde and the Refuge de Venasque.
Looking at the dossier, it seems that whomever put the information together wants the focus to be on the trail from the Refuge to the Port de Glere.
My question for her partner would be : does she follow the rules and sign-in, plus pay, at unmanned refuges? If it was her practice to stay without paying, that complicates the search.
No wifi at the refuge at any time of year at the refuge, so I'm guessing that her partner expected her to be in wifi range again later on Nov 23 as she climbed higher. I think this narrows down where she can be found - narrowed down even more when it is confirmed that she used the honour system to sign-in and pay.
"During unguarded periods, all of the FFCAM shelters keep an accessible and open part, “the winter refuge”, in order to play their role of shelter and relief.
The use of the “winter” part has been modified in order to contribute to the fight against the Covid-19 pandemic. To use this space, you must bring your sleeping bag, kitchen equipment, your masks and hand gel. Wearing a mask is mandatory, in this place and in the presence of several people, as well as respect for barrier gestures. An attendance book in the winter refuge is to be completed upon your arrival.
You will be able to enjoy the FFCAM shelters in complete safety, without forgetting to pay for your overnight stay, which is essential to maintain the services offered."
Accueil, Refuge de Vénasque