Starlet gc said...
My best advice .... especially for a teenage girl will be to see a sports nutritionist to get a proper diet sorted for her height/weight/ training needs.. and also get her to take iron supplements and possibly magnesium..shouuld fatigue start to kick in. Endurance training is taxing on your body and takes a while to start building.
Golden rule - be sure to eat low GI complex carbs and protein. You need slow release energy so you don't spike - whilst protein for muscle building/ repair!
One word for all of these things...... Spirulina. Natures richest source of protein, iron, magnesium and almost every other vitamin and element. A true Superfood! Better than protein shakes and multivitamins by a long shot.
I swear by this stuff, my wife even knows when I have run out just by my mood and appearance. She comes home with a fresh bottle and says 'I could tell you run out you seem a bit flat'.
If you don't know about this stuff already do some reading, speak to a Naturopath. They use it to treat the sick, the Cuban and Chinese olympic teams use it and it's use as a food dates back centuries. It's natural, cheap and is amazing! You can even buy it from Coles these days. Been taking it since I was 18 and probably will for the rest of my life.
An interesting start to your research if you are interested is at
en.wikipedia.org/wiki/Spirulina(dietary_supplement)