Her con was that her company had machines that could do all the analyzing automatically in seconds, it wasn't than blood analysis had predictive value for at least some diseases.
I don't think that even back then anybody disputed that at the very least doing DNA sequencing of the cells found in blood could predict the likelihood of certain diseases for a person, as the concept of some people having a genetic predisposition for certain diseases was already accepted at the time.
The scam was the "magic" machine that could do it fast and cheaply, not the concept that it can be done.
