Man - you were treated perfectly wrong by that nurse. But she did say something that was ok, in that you need to eat stuff that takes longer to digest, protein and whole/raw fruits veggies.
I'm not sure if you are diabetic or not. Eating sugar at lunch made what you felt worse because this pumped up your blood sugar level high and then it. VERY FAST, causing the 'low blood sugar' feeling, even if the level went from very high to normal.
Because you had this reaction, I think you are not diabetic, but if you continue to do this sort of thing, yes, you could run the risk. Feed yourself right and you can avoid diabetes for a long time.
And you won't have to deal with a nurse that has such a bad attitude.