I can understand your concern. I'm sorry to hear about the difficult time. But illness, if approached with a positive mind, can be a learning experience.
I'd suggest that you check out the Hippocrates Institute in Palm Beach, FL. I lived and taught yoga in South Florida, and this institute is well known for helping treat people of terminal illness naturally, based on diet. Of course, it doesn't work for everyone...but it might be worth looking into. Basically, the idea is to eliminate stress so that her body can heal itself. They feed clients a strict diet of raw foods (which are yummy!) and juices, including wheatgrass...and teach them about well being in a 5 week course.
Curing a terminal disease naturally requires a complete lifestyle change. Is your friend's mother willing to do that?