Welcome to the Forum!
I am sorry to hear of your daughters diagnosis. Take her treatment one day at a time, it does get easier. Explain to her the importance of eating all the food that you have prepared for lunch. Talk with the school nurse. Make sure she carries something for lows, a small pack of raisins work well or one individual roll of sweet tarts, as they taste better than glucose tabs and are much cheaper. I wish you both well.