I used to have this same problem, I used the liquid stuff that was mentioned in a previous post to make myself stop. It does work, although everything she touches (food) will taste like the liquid stuff. Its horrible. I quit eating.
My little sister had this problem now, and she has done very well with it, just eats everything wtih a fork.
I hope this helps.
Good luck!!!
You are correct in thinking that this sort of behavior usually serves the purpose of reducing tension. It develops into a habit pattern, an almost 'automatic' behavior. Like any habit, it is difficult to change, particularly in a child so young. This is due to the fact that young children have limited cognitive abilities, particularly in relation to altering such behavior. From a behavioral perspective, one option you have is to cover her hands while at home with cotton mittens of gloves. This obvioulsy interrupts the activity. Over time, the habit is broken. You can't employ such options outside the home, but usually thse behaviors are more of a problem outside the home than in..If your daughter bites her nails outside the home as well as at home, it is worth using one of the liquids (STOP; No Bite; Bite No More; Thum) that are readily available to apply to the fingers. These preparations are bitter-tasting and immediately cause the child to interrupt the behavior, allowing a moment of thought to interrupt the impulse to bite. If you think your daughter is unusually anxious or tense, arrange an evaluation with a mental/behavioral health clinician.