Do you know that most health experts recommend that a reasonable objective for weight loss would be between 1 lb to 2 lbs per week? Rapid weight loss, losing 3 - 4 lbs per week, is advised against as that is when significant health problems can occur. "The risk of developing gallstones is 15 to 25 times higher in patients experiencing rapid weight loss than in the general obese population."
If Terri lost 100 lbs. in one year, then that is within the recommended weight loss goals; if she was 100 lbs overweight, and lost 100 lbs in one year, that is 1.9 lbs. per week.
If she experienced rapid weight loss, then it is likely she should have developed some kind of noticeable health symptom. In that case, one would think since Michael Schiavo is a nurse, he would have had to bring her to the E.R., as pain from gall stone attacks, for example, cannot be hidden as though one only stubbed their toe.
Just to clarify something in your last sentence, Michael did not become a nurse until after she fell ill.