She will need more insulin than normal, the DSN can help you sort out the ratios. It’s also very important to check for Ketones regularly say if the reading is above 12mmo/L, have you been given ketone blood test strips or urine strips? You should definitely get the blood testing ones as they are much better. This link explains about diabetic ketoacidosis I was told by my DSN if my ketones went above 2 to go to hospital as it was new to me and obviously my sugar would be all over, I’d definitely say the same considering she is new and so young. Drinking lots of water would also be a good thing for her, as it will help to high blood sugars a bit better.
Hope she feels better soon