Unfortunately, my almost 4 yr. old daughter picked up this NASTY habit from me...I'm a nail biter, have been much of my life. I CAN stop, IF I put forth a very concise effort too. When I noticed that she was starting to follow my footsteps...I stopped...it was actally pretty easy to stop at that point, considering I knew she was modeling my behavior. I DO still notice I put my fingers in my mouth and "play" with my nails, but haven't been biting them. Anyway, my stopping and her seeing my nails get longer has motivated her to "have pretty nails like mommy." And I told her if she lets them grow, we will go to the "special" nail place to have our nails done together....she's EXCITED about that. BUT...she's still biting them, however, she seems to be aware when she's doing it...because often times she will say, "mommy, I'm biting my nails, I don't know why." So to try to "help" her stop I went and got a product at ULTA, called Bite It...it goes on like a polish (clear), but taste NASTY (I tried it myself to see) :) I just applied it yesterday so not sure if it will help, but so far, I haven't seen her with her fingers in her mouth at all. Not sure if she's attempted or not, because she has yet to say anything about the awful taste. :) I figured I would try it, at see what happens. I had a similar product growing up, that was suppose to taste bad, but to me tasted like bananas...so it didn't help me at all, I LOVED having it on. :) I'm hoping we have better luck with this one, as this one is AWFUL. Good Luck to you...and like some of the posters mentioned, it may not be anything that we (as parents) can control...it might be something that she will have to decide to stop on her own.