Welcome, this is a wonderful site and you will get a lot of support and information here.
I think it's great that your Mum is taking the supplements you mentioned and on the organic diet, my Mum did the same for a few months (she still is on the organic diet ), she also took the vitamin C IVs but was told by the doctor to stop them when she started chemo, and she took Chinese herbs (my sister is studying to be an accupuncturist and was able to help her with that). I believe all that helped keep the cancer
more or less stable and strengthened her immune system which helped her recover quickly from the chemo.
As far as prognosis.... I believe the statistics out there are outdated. There are some new drugs (Iressa as an example, and Tarceva currently in review by FDA) which are used for advanced stage cancer and to which for Iressa approx 10% of patients (30% of non-smokers) respond i.e. have => 50% shrinkage (some very dramatically), and proportion stay stable for several months to several years, these drugs have mild side effects compared to chemo.
And as you see on this site that many of the members have outlived their prognosis. My Mum was told in June that they don't know if she will be around on Christmas, but now less than 2 months away from Christmas, she is in great shape, very active and energetic, has no symptoms, her tumor has shrank more than 30% with Iressa, and she is planning a trip to Switzerland for a couple of months to visit and take care of her 96 year old mother.
It's great that you are so proactive with your Mum... I remember when my Mum was first diagnosed, I spent most of my days on the internet...
I thinks there are a lot of options now and there are new drugs (such as vaccines) in the works, and who knows...maybe in the next few years there will be a cure for stage IV.