Hi
@Inour , how are you taking your blood glucose readings?
Ideally you should check your sister's blood glucose before she eats, then check again 1hour after eating, and again at 2hours after eating to see what effect the food is having.
Blood glucose levels can rise very quickly when you eat so (again) ideally, she needs to be injecting rapid acting insulin approximately 20 minutes before she eats to give the insulin a chance to start working.
Did your medical people give you any advice about carbohydrates or general dietary information?