In some cases, it may work. The reason is does is not founded in sound scientific evidence that has withstood the test of well designed studies. That doesn't mean it doesn't work, it just means that it's chances of working for your aunt are by no means assured. The biggest danger of such treatment is to those who forgo proven medical treatments in favor of a more risky, less proven nutritional one. It can mean the difference between life and death, or survival time.
Nutrition can most definitely play a supporting role in the treatment of cancer.
It can impact a persons energy levels, resistance to infection, and more. There are clinical dietitians trained in the proper treatment of different cancers corresponding to their medical treatment. Your aunt's doctor should be able to recommend just such a person if she hasn't already. Contact you local hospital oncology unit for other recommendations. Click on find a dietitian once on the home page of The American Dietetic Association.