Before you immobilize it, please check with her Doctor(s).
It could be they want that little mobility, as a semi-therapy.
While movement is painful for her, the thought may be that as an adult, she will minimize the movement ... and that some movement is needed during the healing process.
Immobilization could cause everything to lock up ... and her to lose total long-term mobility.
I know you don't like to see her in pain ... though be sure that the actions you take are for her good, and not create a further problem.