I am not familiar with the regimen you reference, but am a long time master faster. I would recommend you use the freshest, cleanest produce you can get, organic if possible. You should drink 3-6 cups per day of juice, which may or may not be diluted with purified water of your choice.
As a good general rule, drink fruit juices in the morning, when your body is naturally cleansing, and vegetables in the afternoon when you are rebuilding. Be sure to drink as much purified water as possible during the fast to assist flushing toxins.
Every fasting day you should do a colon cleansing ritual. The simplest is to do a plain water enema. This will help the body to remove toxins quickly and also help to avoid detox symptoms.
If you drink any caffeine, do not stop! Taper off over about three days before quitting or you will suffer the dreaded caffeine headache!
Remember that any body cleanse should begin with a parasite cleanup, if you have not done one recently.
I am doing a three day juice fast starting today with my partner Carlos who is being treated for prostate cancer. The only side effect of his treatment is a very distended belly, which I believe is due to stress on his liver (he is taking hormone suppressing injections) which is causing constipation. I am betting the stomach will be flat, his digestion back to normal after three days on juice.
I hope your cleanse is a good one and gives your mother the energy to battle the cancer.