Two things come to mind. I think the one item that will be most missed in her comments will be the one about "it's human nature to make these gestures and does not constitute a lie in themselves. It when they are repeated that they tip off a lie... (paraphrased)". I think most people are more likely to overlook that point because the "idea" of catching people in a lie is too tantalizing. Her suggestions are real but not ground you can always rely on.
Her opinion is not necessarily universal either. She is talking about Westerners, mostly American and British. These gestures and attitudes can mean very different things in different cultures or even genetic background. Also you have to consider distress reactions. People under shock speak very differently that you would expect due to the need to protect themselves. I've seen more than once people who have undergone huge tragedies in war, and when talking about the losses, and of seeing atrocities, speak with a smile on their face. It isn't necessarily a lie, it's just trying desperately to not lose their mind and that is their psychological reaction.
She has some great points where Americans and other Western native English speakers are concerned, but it's not universal.