I saw the video several times. She was not trying to hit him. It was one of those stupid things that we sometimes do and she just went in his way. She was slow hence he had time to grab it. He could have let go but no, he needed to finish his romantic line first. You know like in old hindi movies where the girl tries to slap the hero who is whistling and harrasing her and he instead tries to kiss her, she fights back, then he lets her go with a smile? Something along the lines.