You can find the icky nail polish in a health food store. My granddaughter didn't like the taste of hand sanitizer after she had put it on her hands, so that might help also. My oldest daughter, mother of my granddaughter, even bit her toe nails! It looked hilarious, but grossed me out! If she was a little older, or if you think it would faze her, you could find a picture of what is inside of our fingernails under a microscope and show it to her. I did that with my oldest daughter and she never bit her nails again. (Inside our fingernails there are microscopic worm looking things, not very scientific language, but it's enough to stop some from biting their nails!) Good luck to you. And if all else fails, go to a health food store and get the yucky nail polish.
I am a mother of 5, ages 28 to 12, and a grandmother of 5.