Hello, I am sorry for the unfortunate experiences your family has to go through because of the disease and treatment. Legs hurting could be due to several causes, it is very important to understand the reason behind the pain. Most common causes include clogging of blood in the veins of leg, disease spread to the bones, weak bones, generalized weakness, etc. In order to narrow down to the exact cause, it is important to be evaluated by an oncologist. Meanwhile please start her on calcium supplements and adequate diet so that she maintains her weight. Hope I have answered your query. Let me know if I can assist you further. Take care Regards, Dr Jatin Bhatia, Radiation Oncologist