AtSea1979 hi, I know it's late and you may have gone to bed but does your dd want to have her hair cut short or even very short/shaved?
If yes, no worries, if no, I would be very careful.
Either way she may not realise what very short hair or a shaven head may look like on her.
Please do not shave it or anywhere near shave, it has connotations of very negative things (e.g. having nits, being ill etc).
More to the point, if it too short she may stand out at school.
PLEASE try in stages, a bit shorter then a bit shorter etc etc so she and her class mates get a chance to get used to it.
This is nothing to do with roles in society or having to have long hair to look like Elsa, it is to do with her feeling comfortable with it and not standing out.
She may say she wants it and then regret it, it would be too late - although of course it does grow back! 
If you get a few inches taken off this week and she is happy you could have it shorter the next time.
My dd's hair is very unruly. She uses a tangle teaser tangle teaser and Avon spray for hair brushing Avon spray
She also washes it every few days with lots of conditioner.
I must admit I do agree with Jada Pinkett Smith www.refinery29.com/willow-smith-hair