Hello,
It is not correct that she cannot eat after the correction (the correction should have corrected for the high sugar), however, you will need to dose her insulin based on the carbs she eats for dinner.
Please follow the Drs advice.
Are you following a lower carb diet with your daughter? A high carb diet can make blood sugars very hard to control (and need lots of insulin). Low carb is safe for children and doesn't affect growth (it is the very high blood sugars that are not safe, and which restrict physical and mental development of children).
If you are interested to know more about low carb and diabetes management, I can refer you to read Dr. Richard Bernstein "Diabetes Solutions". Available on Amazon, if it's not in your local bookstore/library. He is an Engineer who then studied medicine when he was in his early 40s, and specialises in diabetes care. He nearly 80 (still working) and has diabetes for about 68 years. His book is very information and he uses low carb dietary approach as part of his management approach, including for children.
Ask the doctor what to do.