would like to know symptoms of juvenile diabetes

My granddaughter, age 5, has been exhibiting unusual symptoms with regard to unusual thirst. high irritability and fatigue. The irritability almost mimics a bi-polar characteristic...extremely irrational behavior, until she eats, then its as if another person emerges, sweet, happy, polite. She has always slept 10 to 12 hours a day, whether at night with a nap during the day or straight through the night... she has always required a lot of sleep through out her whole life and is extremely hard to interact with when she doesn't get 10 to 12 hours per day.
She was born premature with obstructive and central sleep apnea which resolved itself shortly after she was born. Beta strep at 5 weeks put her back into the hospital for 2 weeks. She was diagnosed with allergy and activity induced asthma 18 months ago. She is up to date on all of her vaccinations, has regular appts with her allergist and is on pulmacort 2x daily, singular daily, with standing orders for orapred and albuterol. Her blood sugar has not been checked, however that is in the works. For now we are concerned and would like some feed back with regard to her irregular behavior.