Honestly, if you can get a 15 yr old girl to be committed to a training plan (something they want to do by their own volition) then you might have a chance in getting them to eat well, but I kind of doubt it. My experience suggests that you just can't get them to eat unless they are highly motivated (generally by athletics and their peer group). So, with all that in mind on top of the 3-4x/wk dancing- I think the best thing you can do is to make sure she's eating a high quality breakfast (eggs and whites) and dinner (lean meats + starchy carbs + veggies) and perhaps the only thing she's not doing now, a protein shake after training and each dance class. Other than that, it's pretty much an exercise in futility. I wouldn't prescribe macros to a 15 yr old girl either, to be honest.