I understand what you are going through.
Your mum has breast cancer stage 4 with metastases to the bone and lung. For stage 4 disease, the treatment goal is palliative. Hormone therapy is being given to control the disease and is continued until disease progression. If there is disease progression, therapy can be shifted to systemic chemotherapy.
Your mum can also be given bisphosphonates (Pamidronate, Zoledronic Acid) to control the bone metastasis and relieve bone pains.
Surgery and radiation therapy can also be options but this can be done on the latter part of the treatment process, once the disease is controlled.
What is important now is to see how your mum responds to her current treatment.
You should discuss other treatment options with your mum's oncologist.
Thanks very much for your help x