Hi, Thanks for writing in. It will help to get her examined clinically to rule out ny serious concern like a clot in the leg viens. Many patients with history of cancers might develop a tendency of blood gtting clotted in the deep veins of leg. This is known as deep vein thrombosis and is a life threatening condition if not treated on time. However this is not the only condition that can cause leg pain and other conditions must also be evaluated for. The pain in deep vein thrombosis is usually in the calf muscles and there is swelling and redness of the entire lower limb in many patients. Please consult her doctor and get her examined to clear douts regarding any potentially dangerous condition. Spread of cancer to the bone is less likey but not unheard of. This requires clinical examination. Please do not worry.