This about daemonettes: They are, by their nature, very perceptive, and have an innate ability to read the deep hidden desires of anyone around them, as well as enough innate telepathy to speak and understand what they are told without actually knowing the language in which they are told it.
Yslivianne immediately notices that the room she's in is nothing like what you'd usually expect from the humans: no visible technological contraptions, no dirt or mold AT ALL, no gold or steel, no skulls, no posh inscriptions in High Gothic or grafitti in Low Gothic... No visible weapons anywhere either.
When she feels out the secret desires of people around, she becomes increasingly confused. These people want weird and convoluted and almost non-humanlike things! In fact, all they think and say is full of weird convoluted almost non-humanlike things!
When this priest guy have said "Civilization" and "Light", a torrent of unfamiliar concepts and numbers materialized in Yslivianne's head through telepathy - instinctively graspable, but way too much to untangle. His other words are simpler, but still terribly convoluted. These people's desires and language make her head hurt.
Normally, it's the Daemonettes who torture people through excessive intricacy!
(That "Light" thing actually sounds vaguely Slaaneshi! That should be interesting, but Yslivianne is kinda overwhelmed.)
By the way, none of the annoying presence of Anathema anywhere - neither in the place nor in anyone's minds. A relief, but...
It's becoming clear that these people have nothing to do with the humanity as Yslivianne knows it. From a strategic standpoint, this is an excellent reason to slow down, go with the flow, and try to orient.