J.M.
Hi!
I totally sympathize! My husband and MIL are nailbiters. So it was about that time 4-4 1/2 that my daughter started. I hated it! But I realized that harping on it would make it worse... and so I waited... and last year, when she was 5 1/2, she asked for her ears pierced... and I made the terms be that I had to cut her nails twice in a row, or about 6 weeks.... and then, even afterwards, I had to continue to cut them regularly... and it worked! A year later, she sometimes still forgets and chews on her pointer finger, but it's never bad and a big part of it is wiggling her teeth and forgetting why her finger was in her mouth in the first place! :) Good luck!