What Causes Fatigue And Insomnia In A Teenager?

My 14 year old consumed too much sugar after school. She s been trying to diet & having less carbs & sugars. She s been extremely moody (what 14 year old isn t) but even more so & so tired, complaining of it often. she laid down this evening @ 7 & doesn t want to get up. SHE NEVER SLEEPS EARLY...she has trouble sleeping for the most part. There is a bit of thirst, but not extra urination...I m concerned about diabetes. ? I m wondering if this is just a typical hormonal imbalance or sugar crash?