My aunt is recently diagnosed with secondary bone metastases from breast cancer, which sounds really bad?

Not curable but ...: Any instant metastasis qualifies as stage IV disease and is no longer considered curable but is manageable. With the many options for metastatic management, time is now years instead of months especially if bone only and er+ also, palliative targeted XRT may have a role for pain control.

Treatable, incurable: I am sorry for your aunt. When the cancer has spread to other area beyond the primary organ-i.e.Breast- it is called stage iv. It is incurable, however treatable and there are many treatment options available-which will depend on the er/pr and her2neu status of the cancer.Bisphosphonates such as zometa or xgeva (denosumab) are available to decrease risk for fracture. Radiation tx is available to reduce pain.