This article discusses some of the effects of no food or water on those who are greatly weakened by some existing medical condition. The worries about how horrible "starving her to death" seem misplaced to me since those who voice them have in mind a starving a normal, healthy individual and not one who has no mental function. Her cerebral cortex is liquid. She cannot feel pain, or hunger, or thirst, because there is no consciousness there. Maybe the nerve endings could react in a way that we could define as "pain", but there's no brain there to register it.

However, when thinking of the FAMILY, allowing her to die quickly rather than putting the patient and the family in the unenviable position of watching her die over a period of time is cruel. Even if the patient does not suffer, the family would.