Hi sillyivy,
I'm a cancer survivor and my father went through cancer for 8 years. I couldn't find much information while we were both going through chemotherapy and radiation so I started a blog, (www.CincoVidas.com) that provides info on side effects, nutrition and wellbeing.
Processed sugar is definitely something that your mother wants to stay away from during treatment. I wanted to share with you a post I wrote on replacements for sugar like fruits, nuts and herbal teas that may help you and your mother http://blog.cincovidas.com/sugar-and-cancer-101. I also did a post nutrition advice from a naturopath whose main focus is on stabilizing blood-sugar levels in cancer patients http://blog.cincovidas.com/skin-flaking-energy-drooping-look
I hope this helps.
Love, strength, survival,
Britta