skinny again

my 9 y.o. daughter has type 1 diabetes, and she was skinny as hell during her diabetic pre-diagnosis. She used to be chubby & bubbly before the onset of diabetes. She regained weight when proper daily insulin injections were issued. Now, due to her frequent hypoglycemia attacks during the past months, our doctor changed her insulin regimen - we only make the injections once a day at night instead of twice and he replaced the insulin with a slow acting one, together with a rapid acting insulin injected whenever her blood sugar shoots to more than 300 mg/dl.
We noticed that she is becoming skinny again and although her hypoglycemia attacks never occurred again after this, we are now facing the trouble of hyperglycemia more often. Is her becoming skinny again indicates that there is something amiss in her sugar level management? We did not not totally ban high carb foods such as doughnuts etc, as we occasionally let her eat such foods once a week as recommended by our doctor as he more concerned for the hypo attacks than the hyper episodes. What do you guys think of this?