p.65, First Impressions
“You have to pay close attention to someone's normal pattern in order to notice a deviation from it when he or she lies. Sometimes the variation is as subtle as a pause. Other times it's obvious and abrupt. I recently saw a news interview with an acquaintance who I was certain was going to lie about a few particularly sensitive issues, and lie she did. During most of her interview she was calm and direct, but when she started lying, her manner changed dramatically: she threw her head back, laughed in "dis- belief," and shook her head back and forth. It's true the questions dealt with very personal issues, but I've found that in general, if a person is telling the truth her manner will not change significantly or abruptly. But you won't see those changes if you're not watching carefully.”
About the underlined part, I think the original sentence is 1) “She lied.” and 2) “She did lie.“ with the main verb stressed. However, I don’t understand how 2) could be inverted into 3) ”lie she did.“ Do the natives sometimes invert a bare infinitive at the front to focus it?
Would appreciate on your explanation.