Hello snowflowr
A combination of Lymphatic Leukemia with Type I Diabetes is not a very good prognosis. Both of these conditions would need to be supervised by a very experienced & qualified Fasting Practitioner: the Leukemia is resolvable, but coupled with Type I Diabetes, does tend to complicate matters.
Dr Shelton was of the opinion that if a person suffering from Diabetes had been insulin-dependent (which is normally the case for Type I Diabetes) for some time, then fasting was not to be recommended, but if not, then fasting would be; this being a man who supervised over 60,000 fasts in all health conditions, and I would not contradict his experience unless proven otherwise.
So your husbands Aunt could very well be right; it really depends on how long she has been insulin-dependent.
If you tell me which Country you live in, I could recommend a Fasting and Natural Hygienic Practitioner who may be of real help.