I think VenusRising has a point, worth checking, there might be more to it.
AtSea1979 re I don't like it as its now too short to tie up but is so long it's still in her face and no doubt will be a tangled mess of hair and spag bol by later!
I think a lot of other posters did mention this could happen.
Re Those who suggested a tangle teaser, we have one, they aren't much use for thick hair as DD gets impatient after 10 mins and only a few layers have been done.
My DD has very thick hair and it is hard, we sometimes start at the bottom and work our way up, by that I mean brush the lower 2 inches and then got up two more etc. This is because starting at the top the knots get matted in and very hard to removed. We sometimes use a spray to help de tangle and we wash with conditioner often (my son's hair fine and we don't use conditioner on him but dd and I could not wash without a separate conditioner, an all in one shampoo and conditioner does not work!)
It sounds like you were not happy with your hairdresser and their views, maybe find one you feel happier with next time. Some are better than others. Ours comes to our house and is lovely.
Just for the record I had mine cut short at about age 12 and was devastated, hair really is part of identity.
Scarydinosaurs I am sorry to hear your experience you are not lost, you are you! Please can I respectfully suggest seeing a counsellor because there may be other issues. I have seen a lot of counsellors over the years (anxiety etc - this was not related to hair). But counsellors did really help.
I think lots of posters are reflecting that back with their own experiences. I've 'threatened' to get dd's hair all cut off, drives me mad, I would never do it because it really is a part of her identity and her body and I'd rather it was a bit messy (read really quite messy - which makes me very uncomfortable) than she felt really uncomfortable with it.