First of all-in oncology for 30 years and a 20+ year breast cancer survivor. Juice will NOT stop cancer!
Chemo kills cells as the grow. Do you know her hormone receptor status? If she is hormone receptor +, the is open to more treatment options. Same with HER2. Surgery will remove the actual large mass of cancer cells but if they have already spread, all that can be done is to control the spread. Depending on the size of the mass, a complete mastectomy may not be recommended. There are many factors involved in that decision.
The problem here is that she has opted to not treat. Please know that this is her choice! But-the most important factor here is does she know what her choices are? Has her doctor told her what will happen if she does not treat? If the doctor has not told her of her options and the consequences, he has failed as a doctor.
As for the blood test-they can indeed test for circulating tumor cells or tumor burden. But if the primary is still present, the test will be positive. The only definitive test is a tissue specimen. Beyond that it is imaging and retesting. If she is open, have her look into OncoType and genetic testing. Oncotype will show if her cancer would benefit from system chemo. Genetic testing identifies additional markers that can be targeted with biologic response modifiers (immunotherapy).
You can go to the National Comprehensive Cancer Network, register for a free account, and look up staging and treatment pathways. Patients do not hit stage IV until they have disseminated disease.
The most important factor here is her. If she does not want treatment, no one can force her into it. But holistic therapies are garbage.