I had a foster with thyroid issues, and he was on a high dose of meds for a while when I first got him. After a while, the thyroid started to get under control, and the medicine amount got lower and lower. Within time, it was so minimal, he was almost totally controlled, and on 1/4 of a pill once a day. It wasn't that expensive of a medicine either, and you may be able to get it at a Walmart cheaper than at the vet office. I'd check there or a Walgreens if you have them (they get the $4 Rxs, so maybe since it's an older drug, they may have it??).

I will keep Sydney in my thoughts and prayers and hope that she will be ok and that whatever you choose to do, she will continue to thrive and be a healthy girl!