Glad to hear your DD is starting treatment. I remember hating the way I felt when I was sick, always tired and my heart would race when I got into bed...yuck! Anyway, just a word of advice, I was on Inderol (propranolol) to regulate my heart before my treatment and it blocks potassium absorbtion so I would have terrible "charlie horse" type cramps. Make sure that your DD gets plenty of potassium, eats bananas, takes a suppliment, etc. to help prevent this side effect.
Does your DD have tumors/goiters on the thyroid or is it the thyroid itself? I had two large tumors and the actual thyroid was "turned off". I had the radioactive iodine and it destroyed the tumors but left the thyroid alone since it wasn't working and didn't absorb the iodine. Because of this, I do not have to take synthroid and my free T4 and TSH levels are normal. I say this to let you know that DD might not have to take medication forever if she had the same type I had.
Hugs to you and DD and let me know if you have any other questions.