"I didn't know about this world as a kid- learning this is a very recent development- but I definitely already believed in ghosts." She considered for a moment and said, "but all children do, don't they? Before they're socialized out of it and taught to only believe what's in front of them."
Unless it was the unseen as taught by a priest, of course. Luna had never understood how everyone around her could believe there was a supernatural man who lived in the clouds, but that ghosts were a step too far.
But now she knew that they both were equally true, and far more than that besides.