Re: Please tell me why...
Here are a couple suggestions from different angles:
1) Get different kinds of combs/brushes and let her choose which one feels the best.
2) Do her hair in front of the TV
3) Admit to her that sometimes it is going to pull a bit but that is part of having longer hair and excessive drama will not be tolerated. Then implement some kind of reward/punishment system based on her behavior. If she only cries for you then it may just be a habit or control issue and not about any pain.
4) Let her do her hair first, and then you "check" it
5) Finger comb her hair before using any brush or comb. You'd be surprised how many knots can be worked out very gently with your fingers.
6) Always firmly hold her hair above where you are combing so any pulling is not on her head.
7) If she is articulate enough to answer, ask her what others do differently than you.
Mom to DD (02/07) and DS (06/10)