Wild theory: maybe she is unhappy with all the changes and feels like she has no say in anything, and this is the only way how she can get some semblance of agency.
Did she want the school change? Did she have a say in which school she is going to? Do you believe her when she says she can't do something, even if it doesn't make sense to hsyou?
I'm asking the last question because for 35 years, it was not enough if I told people something is too much or I didn't like it. They didn't feel that way, so obviously I was just being difficult. This pattern of accidental gaslighting fucked me up big time.
I'm still in therapy for that, and I still feel unexplainable resistance to doing some things. Nowadays, with the help of a therapist, I found success in not pushing myself, but instead asking myself why I have this resistance. The key is that I'm willing to drop whatever I'm trying to do.
So maybe stop pushing and trying to convince her, and find ways where life currently is difficult for her and work with her to make it less difficult. If she is burned out, time may be the best cure.