What kind of diet should a thirteen year old female that is five foot nine inches go on?
That would depend on how much you weigh, not how tall you are. A
5'9" girl that only weighed 110 pounds would look anorexic. You can
not judge your weight based upon what some little 5'2" snot weighs
and think you are fat because you weigh more than she does. In 10
years she will be gushing about how she always wished she was tall
with long legs like you. Unless there is a determination of morbid
obesity (by a medical doctor), there is no reason for any kind of
diet other than normal nutrition.
Get about 1,500 calories per day, and most importantly, do
approximately 90 minutes of simple, light aerobics (like a easy fun
walk in the park, throwing a Frisbee, skating, or playing tennis or
golf) and you will be healthy, trim (but not skanky skinny) and
well toned without being "muscular".