"I'm going to guess that...whatever did this is actively trying to keep us lost."

Safe bet. Obvious, really, but it's the first step to getting where they need to go. Assuming it's sentient, maybe there's some kind of clue to what it's after, in the way the walls looked or the intensity of sound. She keeps sneaking glances back to York, looking for green eyes or any other sign that he's losing himself.

Or, heck, if he hears voices, they may tell him what's going on.