This picture is confusing. Is it possible to punch backwards like that, in an underarm fashion? This looks like an aggressive move. From the picture it looks like he shouldered her from behind and her left arm went forward, and his right(ed). arm went backward.....from the rotation resulting from shoulders colliding.

Either way it looks like he ran into her from behind (which is either bratty, clumsy, or both). I'm not saying he didn't punch her, but this picture doesn't make it look like a punch.