Suit yourself. I read Cruzan, and the Shiavo material, and all of it is phrased in terms of respecting the patient's wishes. Your blather that my spouse can her assert her wishes over mine notwithstanding, she can't.
Your statement is not true, the decision to remove or continue life support, in absence of explicit documentation from the patient, falls on the next of kin.
If no document exists stating Terri's wish not to live being sustained by artificial means, then no document exists to the opposite either.