I agree with jdtm. You should mention this to your child's pediatrician the next time you take her.
Pullling out one's hair is called Trichotillomania. It is an anxiety disorder. I might suggest you google this phrase to learn more about this issue - "children and trichotillomania". You should be able to find lots of information on the internet. It might be wise to mention this to your daughter's pediatrician on your next visit. I hope this helps ...