Kids of this age do this chewing and sucking. For some it is soothing, for others it is just a habit. The obvious solutions are pony tails and cutting the hair short so that she can't get it in her mouth. You could also try distracting her from doing it by focusing on when she does it the most. When watching TV??..falling asleep etc??? Offer another soothing option like hugging a soft lovey toy. Don't be surprised though, if when you take away the chewing on her hair, she starts chewing on her sleeves or the toy itself. I is a normal stage as long as you think that she is not overly anxious or stressed.
Please let me know if you need more information!
Take Good Care! Nancy