Asleep (after Niall's death, revived by Cabeswater
Dream creature (by Niall Lynch)
In The Dream Thieves it is indicated by Ronan that she is a dream:
"He was brother to a liar and brother to an angel, son of a dream and son of a dreamer. "Later it is in fact proofed that she is a dream, dreamed by her husband Niall Lynch when the gang visit The Barns and find her ageless, paralyzed and dusty.
Ronan "brings her to life" by making her live in Cabeswater.