Sounds as though she was clinically terminal. Most patients in that condition voluntarily stop taking nutrients, but do crave hydration.
A sad story, and sorry for your loss. But it is totally irrelevant to the point of causing death, initiating death, with a starvation process.
But hers was a hydration and starving death. True she was terminal anyway but your point that freezing to death would be a better way to go is not something that is within the power of doctors to effectuate for patients whether they are terminal patients or patients being kept otherwise alive by tubes.