i'm not so sure about this. she's put in years of work with a vocal coach and has a pretty extensive warm up routine that you can find on youtube. she's got some of the best pipes out there right now. it seems like her losing her voice is more related to being sick than poor technique. but its all speculation. only she really knows.
im' not really faulting her technique so much as the strain she puts her voice through. Yelling an A5 is going to cost you no matter how well you are trained, her style is hard to keep clean.