My Niece Was Just Diagnosed With Stage 3 Breast Cancer,

My niece was just diagnosed with stage 3 breast cancer, I don't know too much more because she is just getting started with her appts. I guess they, also, found a spot in one of her kidneys, plus she had a tumor in her brain at age 4 & returned at age 12 years. She is age 42 at this time, I'm just wondering what her chances are of living a long life. I know its hard to tell but I guess its so hard to understand why this young person has gone through so much in her young life.