By that reasoning, "shoot me if I ever get like that" could, theorhetically become justifiable right-to-die.
(4) STATEMENTS FOR PURPOSES OF MEDICAL DIAGNOSIS OR TREATMENT.--Statements made for purposes of medical diagnosis or treatment by a person seeking the diagnosis or treatment, or made by an individual who has knowledge of the facts and is legally responsible for the person who is unable to communicate the facts, which statements describe medical history, past or present symptoms, pain, or sensations, or the inceptions or general character of the cause or external source thereof, insofar as reasonably pertinent to diagnosis or treatment.Under that exception, Michael, as her husband, could present her out-of-court statements while she is unable to communicate, regarding her treatment (whatever treatment may mean here).
I'm not sure if that's what allows Michael's testimony about her intentions. I'd need to read some of the numerous appellate decisions. Anyway, just because a statement is generally hearsay, it may nevertheless be admissable.