Stage 4 is the worst if I can remember. My wife had old age leukemia and was treated with steroids by her leukemia doctor to bring up her count. I do not remember the drug, but she would go in for a check and a shot every month or two.
My wife eventually passed away from lung cancer which matastisized to her brain, not sure if the cancer and leukemia were related, but she had a brother that went in much the same way.
If you are inclined, you may want to read some of the papers published by Dr Kathleen Sazama, now with M D Anderson, Houston, or have her oncologist at least look to see if she has written anything useful. Kathleen has published over 200 papers on cancer of the blood, but maybe it applies to younger folks.
M D Anderson is one of the foremost cancer hospitals in the world, but it seems like your friend may be too far gone. Don't count on any magic potion or cure from Mexico or the internet, some make outrageous claims, but few are successful
May the Lord bless your friends mom and relieve her pain. Often prayer is the only solution.
Her oncologist can reach Kathleen at the M D Anderson web site by email