I think it depends on how you suck your thumb I stopped at 11 and my teeth are fine, slight overbite My cousin was similar and he had terribly stuck out teeth and years of braces etc I agree with getting the second opinion, but for what its worth I don't think it's cruel to get her to stop as long as she has some other way of self soothing which I'm sure you will help her with. Stop and grow didn't work for me, I basically stopped when I felt it was time, not very helpful for a little one, sorry