Basically, to over-simplify severely, instead of taking criticism as a way to improve, she took it as an attack, which I think was part of what made Theranos insular, overprotective. It would be a bridge too far to link it to the cheating.
So, one important criticism of Theranos, which was made at various points starting very early on, was this:
"If a substance is present in the patient's bloodstream, you still won't be able to detect it unless it is also present in the blood sample."
Theranos was always offering a product that was not even theoretically possible. Blood samples must be large enough to contain at least one molecule of whatever you're trying to test for, if it's present. When that's what you start out with, how are you supposed to "take criticism as a way to improve"?