I just watched the 'handshake' video with the commentary. I don't think there's a handshake, I think she put out her hand in a 'stay back' gesture and he grabbed her wrist. At that point she was already pretty quickly backing away from him so I don't think that a 'handshake' would be a logical/natural gesture in that situation. She also could have been trying to hand him her phone or wallet saying "Here, take this, just don't hurt me."
IMO, either of those is a much more logical scenario than trying to shake hands with someone you're backing away from on a dark, deserted street. Unfortunately, I don't think robbery was ever the intended crime, and the fact that he was able to use her card was just icing on the cake for the predator. I just hate to think what she had to go through before she gave up her pin number.