I think if you're stuck on that question, her manipulation poked through the silver screen and worked on you.

To me the subtext of the movie was that a sociopath's manipulation is so strong that even against the heavy counterforce of the filmmaker's bias, it makes it through. I agree with TFA's general premise that the film forces you to confront how easy it is to deceive you -- but it's not the filmmaker who's doing the deceiving. Sociopathic manipulation is about sparking doubt. Gaslighters don't need to prove anything, they just need to plant a "but what if" in some corner of your mind. The fact that the author felt compelled to write TFA at all is ironically a product of that manipulative power.

Another way to think of it is: the documentary makes you think whether, if you were in the room with her in the years that Theranos was operating, would you have fallen for it? If you feel the need to write apologia after watching a documentary that's basically a hit piece, you know the answer.