Obvious question I'm sure, but did you guys try general or targeted radiation? You should look into biologics, see if a hospital in her region is going to be doing any trials. It might be worth checking out, even if it's a guinea-pig situation. Reach out to as many doctors, clinics, just people, as you can.
Here's a link related to breast cancer-specific biologics:
Like I said if all else fails, and I mean ALL else, try IV vitamin C with hydrogen peroxide. There are clinics and doctors that offer it around the country. Some east meets west doctors do it as well, and they do it specifically for cancer treatment. The Vitamin C will boost her immune system to hopefully fight back a little better (but it takes a lot of vitamin C), the peroxide oxygenates, and cancer can't live around oxygen. You will at the very least delay the cancer, get a little more time, help your mom feel better, and give everyone some hope. My mother's prognosis was bad. She was diagnosed with stage 4b cervical cancer. Unfortunately they did not recommend operating, weren't doing any trials, and they didn't recommend biologics. But I also would never have found out about them to begin with if I didn't do my own research; no one tells you about these things.
Try everything you can, even diet changes. My mother knew a man with stomach cancer, he ate nothing but sauerkraut, and survived, for whatever reason. There's always hope. Look everywhere. I heard that smoking marijuana shrinks cancers. It might not completely eliminate it, but if it shrinks it enough, perhaps it can become operable. They make CBD only pills (no psychoactive effects, only beneficial for pain relief and sense of well-being), but unfortunately I think I read somewhere that it should include some THC (the psychoactive ingredient). She would have to do a good deal of it, but they make it in concentrates, pills, candy, gums, whatever you can think of. Even popcorn. It might be worth a shot. Depending on where you live, she can get a medical card, or you could even get one as a caretaker (we have that in California). It would be fairly easy to do considering her diagnosis.
If you guys can't afford whatever treatment you want to try, crowd fund it on kickstarter or some such site.
I can't tell you how long you guys have, no one can. Everyone kept giving my mom different numbers. At first it was 1 month without treatment, 2 with. Then it was 3 months with treatment. Then, it was 15-20% at 5 years with treatment. No one really knew. The number they give you is an average, right down the middle. 50% of women will live above the number, and 50% won't reach it. There's a chance it'll be longer. Unfortunately, my mom chose not to pursue their treatment plan, which was radiation and chemo. It's been 1 month and 40 minutes. I cry everyday. It's been only 4 months since her diagnosis. Be happy you guys have a year, if that's what she has. Regardless of what happens, appreciate every second. I was afraid to research what to expect at the very end. It's different for everyone. It's hard, however you cut it.