She chews on a lot of things... she was trying to chew on the pony's hair too.
But I have seen some chewing on her own hair.
I know, now, about the possibilities of getting some kind of hairball or blockage in her bowels. And yes she has been having problems... one day she passes firm balls and the next she has diarrhea.
Yeah, Its looking more and more like she has a problem. And so far our doctors are not seeing it. But the more research I do the more freaked I am.

Chewing/eating non food items can also be pica
Which can be a lack of zinc.
You might want to have her checked for vitamin and mineral deficiencies.

Good thought... I will add it to my ever growing list of questions

Just thought I would let everybody know... I took my daughter to have her hair cut today. We got it cut VERY short and she likes it.
Yes, she tried to twist it but its too short. So far she has just held her hand on the back of her head. We will see if this helps...

Okay, another persepective just to throw out there. I was an avid thumbsucker until 5th grade. In first grade I retreated to only at night or when by myself. When I sucked my thumb, I liked to have satin or silk or would rub my nose. I knew others who would twirl their hair when sucking their thumb. So my question is does she only twirl and pull on the hair with the thumb in her mouth in a very absent minded way? If so then I would think this is a part of the thumb sucking self soothing behaviour.

My father tried taping socks on my hands at night (I chewed through them in my sleep), hot sauce (I just grinned and sucked it up until it was gone), and countless other things that just did not work. In fifth grade a friend showed me how she quit by sleeping with her hands under her pillow and viola... I learned to fall asleep without the thumb.

I have been very sick in my life and been found sucking my thumb in my sleep (twice) since then.

So, I guess I would evaluate whether it is a part of the thumb sucking activity. If so, it is age appropriate and I would be so careful to shy away from a label and a disease. However, you are there with this and the mother and I am just responding to a short posting, so you will know best!! Good luck.