My dd2 is 10. She is tomboyish and hates anything girly.She is a fairly confident kid, with occasional wobbles,and likes to be a bit different.
About a year ago she asked if she could have her fairly long hair cut off as she really admired the hairstyle of a girl a few years above her in school, which was a sort of very short bob wit a shaved section at the side. hair looked really nice on the older kid but was a big change from dd's hair, so we agreed she would have her hair bobbed to see how she liked it. She did that and all fine, except stbexh expressed annoyance that he 'hadn't been consulted or involved in the decision' (which tbh I largely ignored as he had never, when we were together, taken much interest in how our girls did their hair, and what she had was a bob, not a Mohican).
A few months ago dd2 asked again for the more extreme hairstyle. She was desperate to get it done.I discussed it with her Dad, via text message as he was away somewhere.He wasn't happy and as such we agreed on a compromise which was that she would have a bit of an undercut on one side of her hair, to get used to the more extreme version she wanted-and if she still liked it in a few months time she could get the hair she wanted done. Stbexh was aware of this but after she had her hair done dd2 overheard him talking to his sister and slating me for being 'irresponsible' in letting her get her haircut that way.She was a bit upset by that, as was I, although I didn't mention it to stbexh, as I couldn't be bothered with the ensuing conversation about it.
Dd is booked for a hair cut this evening. She has printed lots of pictures of what she wants and we have talked about wether she is sure she wants it done. she does, and I am happy to let her do it (my view is it's her hair, and that if she hates it she has the summer to grow it out.I would Personally prefer her to have lovely long hair that I can plait and mess with-but she doesn't like that so I will have to content myself with dd1's hair instead 
). stbexh is not supportive of this.He keeps saying he is a 'traditionalist' and has been a bit negative to her when discussing it, accusing her of 'wanting to do it for the wrong reasons and just to look different'. To me, if she wants to look different, and express her personality via her hair, that's actually a good thing.
It is quite an extreme hair cut for a 10 year old girl I suppose.
Would you let her get her hair cut as she wants? I think there will be repercussions from stbexh, if not in person, behind my back I would think. Plus is he right? Is 10 too young to choose your own hairstyle?