And she's fairly well-informed with the basics. That silver and the full moon are, in fact, Hollywood inventions; that fairies fear iron; trolls can turn to stone in sunlight; that pixies can be defeated by turning clothes inside out.
But the characters she's talking with are from the other side of the masquerade and chock full of them. Like (if Wikipedia can be trusted) oni being vulnerable to soybeans and statues of monkeys. And it would, of course, inspire the wildest tales.
So researching a wide base of esoteric creatures and their weaknesses. That's not a topic that you will find in one place. (And should it be just weaknesses like iron, or limitations on their powers? Hmmm. . . .)