:) I have a BA in English, also. ESL teaching, and now I major in English literature teaching, still a college student, although a teacher :).
Now, to the topic:
I used to be extremely sensitive, and my mom's combing and making my braids was a sheer torture.
When she left me with my grandmothers, I did not allow them to brush me at all, and went to school like a scarecrow. I had a great teacher, she was very loving, caring, and gentle. On the lunch break, she took me to the teachers' room, pulled out a soft brush from her shelf, and brushed me slowly and gently, starting from the very tips (ends) of the hair, and going up very slowly, and if I said 'AI!" as it hurt, she took the brush out of the hair, and went lower down, very slowly moving from the ends, up higher to the head, so that hair untangled very smoothly. She was the only adult who did not hurt me. I remember, how my aunt invited me to the theatre to see the Peppi Longstocking play. I was so excited,and wanted to go, but AFRAID, as she said that she will take me there only if I allow her to brush and comb my hair as I need to look nice. Oh well, finally I decided, but I asked for one bonus: I asked my aunt to braid my plaits exactly as Peppi's red braids were braided: namely, the 'tails' curling sticking all the way up into the air. I can still remember, this caused a lot of pain, as in order for the braids to stick up and out, you need to braid them very-very tight, but the excitement was so huge, I was still happy. :)
So, no, your little treasure-girl is not pretending, it does hurt some people much more.
Advice: Do not ever PULL on the brush or comb, but do like my teacher did.
Suggest your girl, that today you will try a totally different method of brushing, and go slowly, as slow as you can: you're a SAHM, right, so you should have some time for it.
If she does not like her hair pulled together into a ponytail, or somehow 'attached', then you can cut her hair only in front of her face, and let the rest of the hair loose along her shoulders and down the back, it will be neat, and away from her eyes and face... go gently, slowly, LOVINGLY!
One more experience I had: I raised a boy, I had him in my family for a year, we could not adopt him as his mom refused to give him away, but he was like a foster kid for us. He was STARVING, this 'mom' starved him to the point when he did not want to eat anymore, he was simply fading away. When my sons and he, they went outside to play, then my boys were storming running around like crazy, happy as can be, but this boy, he just sat down kneeling by the porch, looking around, and finally fell asleep, sitting like this. He was almost 5 years old, but so weak. The biggest pain was bathing. When I scrubbed him with the little towel, he started crying, saying that it hurts so bad his skin. I still had to wash him clean, so i tried to be gentler, but he winced and almost cried sometimes. I did not take it so seriously until when about half a year later, he came to me once and said: "You know, Mom, when I pinch myself like this (and he demonstrated a slight pinching of his skin on the arm with his little thumb and a pointer finger), and when I rub my skin like this (with his palm), it DOES NOT HURT ANYMORE. and he was all smiles. I could never think of his skin being SO sensitive to touch, but now I realized finally that he was not pretending when I was bathing him. Maybe it was because of his starving, I do not know, but it started getting better overtime. It was hard to feed him in the beginning, he was not even hungry anymore, and told me: "I cannot eat these pancakes", and I asked: "Why?"
He had an answer: "Because they are ROUND!" "Okay," I said,"I will make your pancakes square then", and I really made them square, or cut them in half to make triangles. The trick worked, as he could not come up with more convincing ideas on why he 'cannot eat pancakes", and in several months, although eating not much at one meal, he asked right-away: "May I get something to eat VERY SOON again?" He was munching indeed.
I cried a lot, looking at him, but we got him back to life.
I know Your daughter is not so sensitive because of starving,and I was fed well also, when my hair was so sensitive to touch. But this is real, please know it: it hurts.
The last note: my son did not allow anyone to touch his hair, EXCEPT for me, his mom. You know how people like 'petting' the kids on their heads... my boy ducked down on the first sign of such a friendly petting coming, and ran away to take a different position in the room. sometimes he even politely said: "NO!" but his firm voice was very convincing.
So, please, have a lovely environment at home, and also, I think, to gain your girl's trust now, after so many sessions of painful hair-brushing, maybe if you ask her to brush YOUR hair, to make it a mutual experience, maybe it would help a little to restore the peace, trust, and love during grooming :)
I wish you both all the best, T.!