Just so you know, when I was around her age, I stayed awake just so I could see who the tooth fairy was once and for all. As I laid there, pretending to sleep, I saw my dad come in and put the money under my pillow. The next morning I played up the fairy angle so hard because I had ZERO intention of missing out on cold hard cash in the future. My parents ate it up.
My gal lost her first tooth recently. She left a note and signed it with her full name, and "the one on top of you." When I asked what that meant, she explained that the tooth fairy would crawl under the pillow and read the note there. Kids' imaginations are awesome.