How to stop your dog from barking at the door!

Interesting video there. My dog doesn't bark so much at the door, but she barks at certain people who come to help us. There is this lady who comes in to iron our clothes and for some reason my dgo has taken a dislike to her. She barks her head off when she sees her. I should try this technique on her with that lady's cooperation. This is only person choco will even bark at.. it is kind of weird and I do not understand why she does this with this woman.