How long should a woman with a fractured hip, osteoporosis & Alzheimer's exercise or walk?

That would depend on her age and other health issues. Only a doctor or physical therapist could tell you that - after knowing all of the medical history.
Carol

Walking is a good thing, and it may let someone stay in assisted living vs skilled nursing, and also just help relax and relieve agitation. Even at age 85, it may be worth tryint to treat the osteoporosis medically. If they did internal fixation of the hip fracture, that one will probably not break again, FWIW. Hip protector pads are an option too.

My mom had hardware in bth hips after two separate fractures - she had poor tolerabce of meds, unfortunately, and also a wrist fracture - but after subacute rehab and home modifications to make it safer, went back to live indpendently for several years after that. She used her walker carefully and faithfully, as she REALLY did not want to go back to the hospital for another fall. The hips never gave her trouble again. She never got back to walking well after she fell due to an MI - no fractures, but very weak muscles (probable statin overdose) and that was one of the hardest things for her to deal with.

I'd vote for keeping her walking as much as feels good to her as long as it's reasonably safe.

I'm all for the elderly walking for as long as they can. I also know this can be dangerous and so the pros and cons must be considered very carefully. If she could not walk would that greatly affect her quality of life? I think it depends on the individual. I would do as Carol says and talk to her doctor.

miz