Sorry, but the advice to "look up any specialist, is worse than none at all. Patients with thyroid problems are seldom lucky enough to just find a good thyroid doctor out of the blue. We have to search diligently to find a doctor that is willing to test and adjust FT3 and FT4 levels with whatever type of medication is required to relieve symptoms, without being constrained by resultant TSH levels. A good thyroid doctor like that is very hard to find. If you take the time to hang around the Forum and do a lot of reading, you'll quickly find that out, along with much more.
Not sure how it works in Atlanta. But in the uk you get referred to an endocrinelogist via your doctor. or you can go private and pay for to see a specialist in thyroid disease. I too have thyroid and when i have felt all your and your sisters symptoms the doctor has increased my thyroxine and i have improved. Maybe you need a medication incresed. Best to speak to your doctor, but at the same time just look up any specialists in your area via the internet.
I don't have any recommendation based on personal experience, either myself or other members, but I have sent a PM that gives info on two doctors in that general area. These two came from the Top Thyroid Doctors listing. While looking for a good thyroid doctor for someone in your area, I had previously found these two doctors. To find out more about them, I called their offices and asked to speak to a nurse, prior to making an appointment. I then asked the nurse if the doctor was willing to treat a patient by testing and adjusting levels of the biologically active thyroid hormones, free T3 and free T4, in order to relieve symptoms, without being constrained by resultant TSH. I also asked if the doctor was willing to prescribe meds other than T4 types. I got satisfactory answers to both questions.
As for your sister, the purpose and potential benefit from a Combo T4/T3 med like Armour is to increase the level of the most important thyroid hormone, which is free T3. This is frequently necessary when a patient's body is not adequately converting T4 to T3. In order to assess whether your sister's continuing symptoms are due to inadequate dosage of meds, or a need for a T3 source as well, we really need to get you to post her thyroid test results and reference ranges from the lab report.