Hi I agree with what Katie said. Fine a nice women's hair dresser and get it cut in as feminine style as possible. Other things you should do is get an eyebrow wax and get the beautician to give you a nice feminine curve. Also a Eyelash Tint (Blue Black is best) will give your eyes more definition.
A little makeup will be good. Girls your age are well into make up. Also don't frown so much , when you smile you look very feminine, not so when you scowl. Also look at the way young girls hold their hands . Some of the pictures highlight the masculine features
JudithLynn