What would you do?

[Garland]

I think the problem is this: discontinuing medical treatment is a passive choice - they're not actively doing anything, just refraining from doing more. By administering a lethal injection or somesuch, they'd be actively taking steps to kill her. They go from omitting to do something, to choosing to kill by a deliberate act. It's a technical distinction, but one is homicide and the other is merely the exercise of medical discretion.

If there's absolutely no possibility of her experiencing any sensation - conscious or unconscious - then I understand the decision.

Not administering medical treatment is a passive act. If the tube had never been inserted, and a decision was made not to insert such a tube, then your point would stand. Removing the feeding tube is in fact a deliberate act meant to cause her death. I see no distinction.