I need help.

My 7 year old niece has type 1 diabetes.I'm new to this diabetes thing.I put vegetables and fruit like raspberries and strawberries and made fruit popsicles to keep her blood sugar down but it's been very hard to do that because My sister keeps frying chicken and buying pizza everyday.There was one point where Her blood sugar was 400+. Sometimes it would be 200-300.The only thing thats been knocking it down is the green tea with a pinch of cinnamon in it. Me and my mom are trying to find a dietitian.I would like to know how many carbs,sugars, and proteins should a 7 year old have everyday and is fried chicken good for someone with diabetes? any type of tips and advice would help.