I agree with-the others--Sensory Integration Disorder.
It can be a stand-alone diagnosis or go alone with-other things, such as bipolar or Asperger's.
After a thorough work up and good diagnosis, she really should get on medications. I would find a way to negotiate with-her. Because she already told you that she wishes she could control herself, you know that deep inside there is a normal girl, hating the way she feels. And she takes it out on you, because there you are, right in front of her.
Would she take it well if you printed out something on S-I-D?
Make sure you buy her only soft things with-no scratchy tags, or allow her to cut off the tags. I can only wear soft things, although I'm not bona fide Sensory Integration Disorder (SID), and I can only imagine how awful it must be.
