Most of these miraculous justifications state that at least one doctor said "the patient would never walk again", or "had 6 months to live". No doctor I've ever known has never had the confidence in their skills to make a definite prognosis like that (and I've known some pretty confident consultants). That's the way doctors break bad news in Hollywood films and bad daytime TV dramas. Patients might unfortunately hear it that way, and people anxious to prove a miracle might make it up, but doctors don't say it. Doctors say things like "his spinal cord is almost completely severed at T7-T8 level. It's extremely unlikely he'll ever get sufficient motor function back to be independent of a wheelchair". Or "On average, people with small-cell lung cancer survive 6 months". Prognostication is something EVERY doctor has doubts about his ability to perform, as each one knows several patients who defy the odds (whether they pray to Mother McKinnon or not). I've seen diabetic patients whose blood sugars should have killed them years ago. I contact their GP, not the Vatican.
Adele Horin (thanks Pharyngula) has another splendid angle on the whole affair here.
At the time Mary MacKillop answered the prayers of a woman dying of leukaemia, there was a lot of static in the air. In China 43 million people were dying of starvation in one of the world's worst famines. Thirty years later in the 1990s, when MacKillop answered the prayers of a woman dying of lung cancer, 3.8 million were dying in the Congo wars, 800,000 in the Rwanda genocide, a quarter of a million in the Yugoslav wars.Very good of MacKillop's ghost to hear and answer the prayers of two Australians amongst such carnage.