Hi J.. My name is L.. I have two children, ages 11 & 8. My 8 year old son grinds his teeth - I first noticed it around the age of two. I asked his dentist about it and the dentist said that the remedy for teeth grinding is to wear a mouth guard, which is a plastic mold that is fitted to the teeth. Unfortunately, with kid's mouths you can't fit a mouth guard, as the mouth is growing and they don't have their adult teeth yet.
I found that that spending some time with my son at bedtime to help him physically and mentally relax reduced the teeth grinding. When he was too young to talk with me, I would give him a warm bath before bed and then rub his feet or scratch his back and sing a lullaby. Now that my son is older, I take 10-15 minutes at night to hear about his day and help him resolve any issues in his mind before bedtime. I still rub his feet or scratch his back, but my singing (which was never great anyway) has been replaced by conversation. On days when I know my son was stressed by playground problems or worries, he will still grind his teeth even with a relaxation session, so I think that stress is really the trigger.
We all experience stress and anxiety, even little kids. Learning to share, not being able to communicate completely, being in new social situations, etc. are stresses that our little ones experience. How we deal with stress takes many forms, and teeth grinding is a classic (and unconscious) stress release.
Check with your dentist on mouth guards when your daughter is older and has most of her teeth (my son is approaching this milestone and I will be getting him a mouth guard soon) and in the meantime, help her to relax.
Take heart, this is a rather common problem and any dentist will tell you that they see alot of young kids with teeth that show clear evidence of grinding.
Hope this helps!
L.