re: Where's the line?
Maybe, if there is no living will it should be when the people willing to pay the bill agree to call it.
I think she is dead but the parents want to keep her "alive" and I suppose they are willing to pay for it. If I am wrong about that and she is a burden on the state it is another issue.
If she is as dead as everyone thinks, she should be euthanized not starved.
As far as the expense and resources are concerned, what about cryo? People spend fortunes freezing bodies and heads in the hope that they can be re-whatever in the future. Is this so different?