Do you have a copy of your daughter's blood work? If you don't have a copy of the lab report, your doctor is obligated to provide you with one, upon request. Always make sure you get one before you leave the doctor's office.
Often when thyroid tests are done, they only test for TSH, which is a pituitary hormone and not reliable since it can fluctuate from day to day or even within the same day. They really need to be testing for the actual Thyroid hormones, which are Free T3 and Free T4. Even if those are tested, they often come back in the very low end of the range, which can cause hypo symptoms for many. I'd also wonder if they did tests for thyroid antibodies, which is very important. Does you daughter have other symptoms of hypothyroidism?
If you could post whatever results you have, so I can take a look at them, I might be able to shed some light.
My next concern would be insulin resistance; again, blood sugar levels can be perfect, but there could be too much insulin in the blood. Insulin is a "fat storage" hormone, so insulin is not utilized properly weight could be an issue.
How many times a day does she eat? What are the portions? What kind of food does she eat after 4? There is alot that can be dome but need a little more info!!