@fairn
Hashimoto's thyroiditis is limited to thyroid gland. If the symptoms remain post thyroid removal and on hormone replacement therapy, this can be a sign of another autoimmune disease in the body. Common associations are celiac disease, diabetes, RA, adrenal disorders, vitiligo, other.
I was diagnosed with Hashimoto's 15 years ago and was OK for 12 years. But 3.5 years ago, I was diagnosed with Systemic Sclerosis or scleroderma that started with Raynaud's vasculitis (purple fingers) and fatigue, then skin thickening over hands. Later on, it progressed to stiff and swollen joints, GI reflux and allergy to many foods. I also was on medications that contributed to GI distress. Need to be careful with medications. Some autoimmune diseases do not respond well to current medications, but new symptoms may develop or get worse. From personal experience, it may be years before another autoimmune condition becomes evident. Supportive care, like anti-inflammatory medications, anti-inflammatory diet, lifestyle modifications may be best treatment.
Autoimmune and inflammatory conditions are diagnosed by Rheumatology. Celiac disease - Gastroenterology. I think good Rheumatologist can do extensive blood tests panel to see what other possible conditions may be causing symptoms.
But let your daughter see a specialist to rule out other causes of fatigue and seek possible treatments.
Please see a link to
https://www.eurekahealth.com/resources/hashimotos-and-other-autoimmune-diseases-connection-en
https://www.mayoclinic.org/diseases-conditions/hashimotos-disease/symptoms-causes/syc-20351855