Hi, Osteoporosis is a systemic disorder and does not particularly affect any specific limbs. I am liable to think, as she is diabetic you are talking about a gangrene foot on the right foot. It should be a type of dead tissue, black in color. It occurs due to poor blood supply and amputation might be necessary to limit the gangrene spread and risk of infection. Osteoporosis can be controlled through biphosphonate medication or hormonal therapy. Along with a healthy diet, calcium and vit D supplementation is also necessary. Complimentary mild exercise and weight loss is essential for improvement and can be followed by bone mineral density test at a later date. Diabetic control is essential to avoid any further complications. Regular medication, proper diet and weight control are essential. If you have any further queries, happy to help again.