If you're skeptical of the concept, that's good. You should be skeptical. Here's an experiment you can try. Say out loud, "I love my wife," or something else you strongly believe; and shake your head "no" as you say it. It doesn't feel natural, does it? That's because nobody shakes his head "no" when he's expressing a positive belief.
After you've thought about it, maybe you and your friends might like to make a game of it. How many of her lies can you and your friends detect in a single video clip?