I don't understand why your daughter won't follow simple rules about uniform when everyone else does. It's not normal behaviour to continue in the face of repeated detentions. Maybe she's mistakenly got it into her head that it's personal? She sounds intelligent, so would probably benefit from some explanations - sorry if you've already done that! In your shoes, I would explain that the reasons are three-fold:
First, issues of preparing kids for the outside world, where they'll almost certainly be part of companies or organisations where there are rules. Also things like team spirit and being part of an organisation bigger than yourself. Secondly, that there are some men in the world who are attracted to children and we'd rather not draw their eye. Yes, we know that we should be able to wear whatever we want and not suffer any consequences, but that's not reality.
Thirdly, repeated detentions will leave a black mark on her record even if she does well in exams. Remember this: The school will give references to universities. Her making such a big issue of disobeying school rules makes her look extremely bad. Tell her that it makes her look as if she thinks she's too special to obey the rules that everyone else does, even if she doesn't think that at all.
I think the onus is on you as her parent to let her know how bad she's making herself look, that she won't get away with such things as an adult - she'll just get fired - and that she is risking a good school reference, whether that's for higher education or a job. If I was a teacher who was asked for a character reference for a job, I'd have to say that she's disobedient, has trouble following simple rules, and is not a team player. Not great, right?
She definitely sounds like the sort of kid who would benefit from knowing all the reasoning behind such rules.
She seems to have developed the idea that this is a personal battle between her and the teachers. Make her see that it's not, based on all the above.