When deciding whether to withhold or withdraw medically assisted nutrition and hydration, or other forms of life support, we are called by our moral tradition to ask ourselves: What will my decision do for this patient? And what am I trying to achieve by doing it? We must be sure that it is not our intent to cause the patient's death -- either for its own sake or as a means to achieving some other goal such as the relief of suffering.
It is not at all clear what the position of the Church is on this matter:
Second, we should not assume that all or most decisions to withhold or withdraw medically assisted nutrition and hydration are attempts to cause death. To be sure, any patient will die if all nutrition and hydration are withheld.[12] But sometimes other causes are at work -- for example, the patient may be imminently dying, whether feeding takes place or not, from an already existing terminal condition. At other times, although the shortening of the patient's life is one foreseeable result of an omission, the real purpose of the omission was to relieve the patient of a particular procedure that was of limited usefulness to the patient or unreasonably burdensome for the patient and the patient's family or caregivers. This kind of decision should not be equated with a decision to kill or with suicide.
Out of respect for the dignity of the human person, we are obliged to preserve our own lives, and help others preserve theirs, by the use of means that have a reasonable hope of sustaining life without imposing unreasonable burdens on those we seek to help, that is, on the patient and his or her family and community.
Our tradition does not demand heroic measures in fulfilling the obligation to sustain life. A person may legitimately refuse even procedures that effectively prolong life, if he or she believes they would impose excessively grave burdens on himself or herself, or on his or her family and community. Catholic theologians have traditionally viewed medical treatment as excessively burdensome if it is "too painful, too damaging to the patient's bodily self and functioning, too psychologically repugnant to the patient, too restrictive of the patient's liberty and preferred activities, too suppressive of the patient's mental life, or too expensive."
And this is the one I'm sure the Church relied on in this case:
Second, our tradition recognizes that when treatment decisions are made, "account will have to be taken of the reasonable wishes of the patient and the patient's family, as also of the advice of the doctors who are specially competent in the matter."
The Church's position on this is very lengthy and complex and it does not do their position justice to merely state they are opposed to death by dehydration. There are numerous instances, included excessive financial burden, where the Church says this is okay.