The lake scene in The Girl Who Wasn't there....

Who or what do you think Luna saw go into the lake? It's revealed that >!it wasn't Aurora as Luna originally thought!< . But then, who was it?

It's implied that Luna was dreaming, and yes Luna does mention very early on in the book that Luna has very scary and often realistic looking dreams. It's brought up in other parts of the book. It's clearly a build up to something - ala the lake scene.

Personally I think the person Luna saw was >!Tansy's ghost!< . Perhaps Luna's subconscious wanted to help >!Tansy!< , despite how scared Luna was of it all. Thus her "dream" manifested in her trying to save someone.