I agree with @coach723 . I would make her comfortable letting her do whatever she feels like, offer foods she likes, and if she seems to be uncomfortable and suffering, put her down. Weight loss with a firm mass in the lower belly sounds like oviduct cancer, but hard to know for sure until a necropsy is done. Many of us do them at home, and some send the body to the state vet to do, but that is the way to find out. Take pictures, and someone here may offer help.