Hello Molly,
After having read your letter I understood we have had similar problems when it comes to wearing things we like.
My mum also behaves the same way your mum does and it makes me quite a little bit disappointed. You know Molly that I give my preference to stylish modern clothing,- so tight blouses and leather trousers, - are a kind of a style I stick to. My mum also thinks that my skirts are too provocative and explicit, I have never thought I would hear such words of skirts that are 10 centimetres below my knees.
I do love wearing fashionable things even those with long cuts on them, I think they really make me more attractive and give me a look of independent, a little selfish individual. Maybe it sounds funny to somebody but not for me.
So, I have lots of troubles with my mum and dad arguing of my clothing, but that doesn`t mean that I`ll ever take their side on this issue. Try and be yourself - that is my advice for you and in short time they will recognize you as an adult person !