What is the survival rate of metastatic melanoma stage 4?

My great person in my life has stage 4 metastatic melanoma. She has always been an extremely healthy person, no health problems (besides cancer of course). She was diagnosed with cancer in September of 2013 and had 6 tumors on her liver. She recently got the news that she has a genetic mutation called NRAS which makes her cells multiply about 7x faster than an average persons cells. Since she has this mutation the cancer spread into a small tumor in her brain, even though she was in an intense chemo treatment with several drugs. Now she has 6 tumors on her liver, and two of them have grown in size, along with a small one in her brain. What would be the survival rate on this prognosis..? Not expecting hopeful answers, just some that have been based on experience or facts would be nice. Thank you.