oh no Gio! Your poor ds and poor you having to look after a sick baby when you are ill yourself (been there, done that, and will again... )
Hot, have they taken her to see gp already? They need to rule out it is some kind of infection. But I expect they've already done this, if this has been going on for a while.
I have no doubt she enjoys her school, but it can still be a source of anxiety. I suffered of gastrite in my first year of scuola media, as I was desperate to please my professoressa di lettere, who was very strict, but I liked her a lot.