My Sister Has Stage 4 Breast Cancer. It Has Spread

My sister has stage 4 breast cancer. It has spread to her bones, liver, lungs. She is in the hospital with a lot of pain from the cancer. She has been doing chemo since July and the cancer hasn't gotten smaller. Her doctor has basically given up. Is there still hope for her? She is a fighter and wants to keep fighting. She has endured so much in life this just isn't fair. Doesn't she deserve to keep fighting?