She has moderate Osteoarthritis where there is wear and tear of supporting tissue called cartilage. This is a progressive disease and causes pain on walking, climbing stairs.
It would be better for her to consult pain management doctor who can asess her. These days there are lot of good treatment options like platelet rich plasma therapy. Even I would advise against giving pain killers.
Next Steps
She should visit a pain management specialist
Health Tips
Ask her to avoid sitting on floor and cross legged