You can't argue that she was PVS, a brain-dead vegatable, and then claim that it was cruel to keep her in a bed. Don't you see how absurd that arument is? The parents said they would take over ALL, repeat, ALL care and cost. So that argument gets destroyed.
If someone wishes NOT to be kept alive, and for their family not to endure 15 years of life-sustaining care, it is cruel to them to keep them alive, whether they know it is happening or not.
Sophistry will get you nowhere.