I really don’t think Bell did it. She wouldn’t have known enough of the stories.
The only person I can think of who could do it would be the blue fairy, but the idea of it being written into the curse is neat. The only problume i have with that is the fact that it was Rumple who wrote the curse so he would have had to of written that in as well but there was no way he could know that there would be one person in town who wasn’t cursed and have it find its way to him.