I've been mulling over comments by AriaAria and BellaBoo83.
It struck me that BellaBoo had assumed the Refuge du Venasque was a hostel style refuge, like the
Refuge du Angel Orus. What if Esther had assumed the same? That would explain the lack of food taken, as a meal could be bought. On the 19th Nov in her social media post she seems to use the words 'caban' and 'refuge' to mean two different things.
From this paragraph, it sounds like she planned 'another refuge' like the one she had just stayed at (Refuge du Angel Orus). There is also a reticence to stay in the more basic caban. Refuge du Venasque is more like a caban.
However, by the time she is on the mountain top, she is saying "Hoping Refuge Venasque has a winter room". At this point, she must have known that it was a more basic caban type hut, as these are the ones that might have a
winter room.
So perhaps she started the walk thinking there was a hot meal and warm bed awaiting, but at some point (maybe googled it), realised it was a more basic mountain hut.
AriaAria was musing why she might have made a snap decision on the peak to head west, instead of back down the path east and towards the refuge. Maybe after she sent this message, she thought 'what if it doesn't have a winter room? It's going to be awful', then perhaps made a rushed decision to come down off the mountain via a different route to the west?
I think it's unlikely she made it to the refuge. Whilst there is no mobile service there, I think if she had overnighted and then continued her walk, there would have been a message sent saying she had made it to the hut and whether there was a winter room etc.