For more info on what she's talking about, see here.
I actually went to a seminar once where the instructor told us about this technique. To be fair, it was one among others. Still, though, he did confer on it a certain validity. I couldn't get into it, though. If negging works for you then, best case scenario, you become a psychologically abusive boyfriend. I just wasn't ready to commit to the abusive boyfriend lifestyle.