Being your fucking self and not giving in to societal standards is the ideal figure for a 15 年 old girl of 5'7" stature. In fact, that's the ideal figure for people of all ages, heights and genders! It's very in right now, and I can guarantee 你 that you'll look HOT with your ideal figure!
It makes me sad to think a 15 年 old is worried about having a perfect figure :|
There is no such thing as a perfect figure. Just be yourself and be healthy, that's the best 你 can do. Don't worry about the numbers on a scale 或者 measurements. There are no 'perfect' measurements.
你 should not be worrying about your figure - unless 你 think that there is something medically wrong - in that case the best person to talk to is your doctor. If he / she thinks things are OK - then don't worry. If the doctor thinks there is something wrong - follow the advise of your doctor.