Do you have any set of exercises to use with individuals who have osteoporosis (this person also has arthritis and cervical spinal stenosis, and according to her Physical Therapist, should do weight bearing exercises, but keep her spine in neutral position, and not lift anything above her shoulders.
I would get medical clearance, a prescription from her PT and have a very close relationship with her doctor
Ultimately she will need to know her limitations and restrictions and be able to modify and implement them.
I would be very clear about your concerns and state them to her
You are under no obligation to have her participate if you feel it’s a risk.