Regretably, I don't see the "religious freedom" argument going very far given the current "freedom from religion" atmosphere.
The only things I can really see helping Terri would be either (1) the impeachment of Judge Greer and his replacement with an honest judge to hear the guardianship case, or (2) some additions to the guardianship statutes to expressly ensure that a judge can't order that a person be put to death before a pending guardianship challenge is heard.
Have they tried to go to the court of appeal and ask for an order directing the judge to stop stalling?