My 87 Year Old Mother Was Put On Oxygen Due

My 87 year old mother was put on oxygen due to lots shortness of breath & fatigue. She has high blood pressure, diabetes, and breast cancer that went to her lung 5 yrs after being diagnosed. It's been three years since the cancer is in her lung but growing slowly. She has several small growths and a 2 cm on in her chest lymph nodes. Some family members don't believe she should be given the oxygen because she is doing fairly well. Your opinion?