So even if it was in the Illidan novel, despite the novels being 100% canon, you wouldn't accept it? Talk about denial.
Good thing its from an even more concrete source:
The game.
10 seconds in.
Elune existed before the ordering of Light and Shadow. By simple logic she cannot be a Naaru, Void Lord, Titan, or Old God.
Sorry if my repeating of the canon triggered you.
PS: The novels are 100% canon. As canon as Chronicle is.