I have a draft medical power of attorney that spells out clearly the desire to be provided food and water. It is assumed by the client that food and water and life saving machines will be provided unless rejected by a living will...not so.
As the this Catholic issue: Know that in the US, the Catholics are split between raving liberals who pick and choose cafeteria style which beliefs they espouse and those who are following the beliefs of the Catholic church. In my area, the not for profit group that does advance directives is run by a nun.
The purpose of palliative care is to make the individual more comfortable, and more functional if possible; it doesn't mean "kill her off." A cancer patient, for example, can receive palliative care even while undergoing treatments such as chemotherapy or radiation which are intended to cure the cancer, or considerably prolong the person's life.