I was hypo for a year before becoming Hyper and diagnosed with Graves. I have been on thyroid suppresants (methimazole) for about 1 1/2 years now and seem to be relatively stable. It's rare to switch, but it does happen. (less rare to have episodes of Hypo/Hyper due to thyroid problems that are not graves/hash) Her endo would know best, but they can run tests to check if it's graves. I agree hypo was much easier to treat/deal with than hyper..but with medication you can get back to normal. The hard part is the toll it takes on your body, both physically and emotionally. Your daughter is lucky to have you.
A lot of people go from hypo to hyper to hypo, many times.
That is how thyroiditis progresses.
Switching from Hashimoto's to Grave's is a different situation. It can happen, but does not very often. It happens when you have developed Hashimoto's antibodies and then after being treated for a while you also develop TSI antibodies which become dominant and it turns into Grave's disease. Then it becomes a contest to see which antibodies can remain dominant.
Hyper does not always mean Grave's disease. There are several reasons you can turn hyper. It is usually short term and then you go back to hypo.
This is a great question for AR-10. He has been diagnosed with both Graves and Hashimoto's. I am pretty sure that would mean he (and your daughter) has tested positive for antibodies for both. I have Hashi and I do fluctuate between hypo and hyper due to medication dosage changes. I can definitly tell when I am hypo, hyper makes me such. You need to be a good advocate of frequent level checks.