D.P.
Hi K.,
I have a friend whose youngest son did that at about the same age. He used to pull the hair out of the crown area and they used to call him "The Fryer." He is now 3 and seems to have outgrown it. I believe it is called trichotillomania. You could google it for more info. I would keep her pediatrician advised if it continues though. Good luck to you and your daughter.