Physics of superheroes is something which shouldn't be discussed scientifically, of course...
In the comics, you see things like Superman, Thor or Hulk stopping a train which normally shouldn't work because, no matter how strong you are, if you don't have enough weight, the train will always push you away.
But nevertheless, somehow they can stop a train that way in the comics.
And if Asgardians, Kryptonians and gamma ray monsters can do that, it doesn't make any sense that a mortal woman can move the face of an Asgardian (or frost giant offspring) by slapping it.