[CAluvdubya]

His arm is in front of her, how does he pull her back? Her facial expression never changes. If someone grabbed me, my face would show either surprise or anger.

It looks more like she lost her balance or footing (maybe heels?) as the group moves past her.

[poconopundit]

You got it right.  Looks to me like Corey was just being courteous to guide Michelle to the side because Corey was trying to catch with Trump.

So he may have held her arm for a moment as he was passing.  That's nothing but simple courtesy in a crowded space.

Looks to me like this Michelle had the look of disappointment on her face that she did not get a chance to ask a question of Trump.  Yes, certainly no feeling of pain.

What a con artist she is.