I understand the young lady's viewpoint and I personally feel that she should be able to wear her hair however she wants. But....(and y'all knew there'd be a but, right??

)
I agree with someone upthread who said she needs to learn to pick her battles. Unfortunately, you can't butt heads with the Powers That Be
every single time you disagree with a rule. And shame on her mother for backing her.
I'm not some mindless prole who can't think for herself. I have four tattoos but the people that just hired me for an executive level job don't know that because I keep them covered in a corporate environment. Not sure if that's comparing apples and oranges; just wanted to state that I'm not on the record as being anti-individual.
But you can't turn your life into some Quixotic quest in which everything has to be just.the.way.you.want.it.
Edited to add:
When I was in high school, the administration had a rule that you had to wear socks. That's stuid, right? We all thought so. But wear socks I did. And I really don't think it stunted me in any way.