Lisa,
If she doesn't want treatment, there's not much you can do except have 2 doctors declare her mentally unfit and force her into treatment (which is VERY unlikely) and besides it would have to go to the courts first anyway. You did mention that she is "end stage" with mets to the lung. There are people here who have been faced with the unfortunate decision to withold treatment and/or nutrition.

Screaming under the train might be good therapy for you. It sounds to me like Aunt Ro has made her own decision on her destiny which is her right. You may need to step aside and respect it at some point.