She was dreaming.
She could tell these things sometimes. Not always, of course. Only sometimes.
She didn't really understand what the difference was between the times when she could innately and immediately sense she was dreaming and the times when she was completely, blissfully unaware of it.
Perhaps it was the way the air felt. The sound that didn't quite make it to her ears and never seemed to come from anywhere specific.
The way things just didn't quite make sense, but still tried to.
The way the world felt smaller than it should have felt, like all the filler and scale her mind never bothered to pay attention to was missing, and the world shrank accordingly.
The dreams when she didn't realize she was dreaming were different.
Either they were so utterly outlandish that her mind must have simply rejected the concept that it cold be anything but reality simply to create it in the first place, or they were far more accurate.