For some reason that reminds me of symptoms I used to have when I was that age. Mine were completely different from hers: I kept feeling as if I wasn't breathing deeply enough, and regularly taking a noticeable extra-deep breath. I certainly couldn't have tied that to any definite cause then, and probably couldn't now, but when I think back to those days, I obviously felt frustrated a lot. Some examples:

-- Except for a few babies, most of the other kids in the area were a little older and more daring than me. There was fun stuff they were able to do, like climbing into the loft of a nearby barn, that was too dangerous for me. I often felt left out.

-- From where we lived, we could see an interesting-looking landmark on a hill maybe a mile away. We decided we wanted go look at it up close but we couldn't seem to find the way there. Whenever we'd set out down some promising-looking road, it would end on private property where there was a grouchy dog ready to confront us.

-- For some reason my mother used to mention stuff that I might have liked to play with, if only we had it. It seemed that either we'd never had any of these items, or they were locked up in a storage shed with a pile of wood in front of the door. I tried a few times to clear away the wood but some of it was in the form of logs too big for me to move. Later the official family explanation for my odd breathing patterns was that I must've strained something while struggling with the log, and that I should be more careful.

I remember sometimes combining bits and pieces of these scenes into a dream -- for instance, that the other kids had gone to explore the landmark, they'd gotten into a bad situation, and now the whole landmark was going to fall off the hill with them in it.

Later, as my situation changed (I lived in a different area, knew different kids, started school, etc.), I remember showing entirely different symptoms. I was easily startled, hated loud noises like train whistles, hated being in the dark, and feared that some sharp object would jump up off the table and poke me in the eye. I'd guess that I was reacting to entirely different stuff then than I had been at age 5.

When I reconstruct my age-5 situation now, it seems as if my parents must've been feeling frustrated at stuff that was going on for them, having trouble coping with it, passing some of it along to me, and not liking feedback from me about what they weren't handling gracefully for themselves. Easier to blame the kid and the log.

My sense is that your friend's daughter has something pressing on her the same way I did, that she can't find words for or that wouldn't be real safe to talk about if she did. She wasn't necessarily abused, though I don't know how likely or unlikely it is that she has been at some point. I think what would help her the most is someone she could talk to or otherwise express herself to, who's not stuck in the same situation and isn't threatened by it. In the beginning that could be anyone willing to listen, though at some point a trained professional might be even more helpful.