I’m sorry, but the video looks like he grabbed her on her upper arm......and this picture looks like lower arm. Sorry, not a Trump supporter, but she doesn’t even react like she is in pain or anything in the video. Could be a faked picture.
I just watched the clip full screen and it does look like she was swung aside to get her out from behind Trump. She was moving between Trump and Secret Service. She got past SS all the way to the left and Lewandowski reached out his arm to sweep her back out to the right so he and SS could protect Trump’s flank. Its those guys job to protect Trump who allows closer access than they would like. If you force or blunder your way in you are going to get moved out.
In military tactics, a flanking maneuver, or flanking manoeuvre is a movement of an armed force around a flank to achieve an advantageous position over an enemy. Flanking is useful because a force’s offensive power is concentrated in its front. Therefore, to circumvent a force’s front and attack a flank is to concentrate offense in the area when the enemy is least able to concentrate offense.