This little ghost girl is not really part of the moonchild world, although she haunts the houses they live in.
Her name is Lily. She doesn’t remember her death, or even for how long she has been a ghost. Lily resides in the attic of the MacLean house, and the kids can see her if she wants to be seen. She seems to be a friendly ghost, and the kids are not afraid of her. She doesn’t communicate, but she can move objects.
The kids sometimes play board games with her, but she often disappears in the middle of a game. Lily seems to be content watching them from her favorite spot (an old swing chair), and they often forget that she’s there.