I'm interested as well. A fairy might be fun! The curiosity and immaturity I understand, but I'm not sure I want the character to look like a ten-year-old. Would a more teenage look or something closer to Tinkerbell work? I imagine that fairies would have access to some sort of intuitive or naturalistic magic. I'm not sure if you would throw that in with the witchcraft stuff or just call it its own thing. I think I might attach an element or other concept to the fairy species to give her a more cohesive identity.