mean you'll probably watch this scene and wonder why she is behaving so hostile while Clint is just sitting there calm as a cucumber. She's impulsive and childish. I think she really wants to get a rise out of him but he refuses to give her what she wants. So her final attempt to break into his anger, get him to show some emotion is throwing the cake down, and yet she still doesn't get what she wants.
But starting at this point with Kat i think was great because then you get to see how throughout the film she matures and grows. I think it's going to be a fun process making her into a character that you can love by the end of the film, even if you love to hate her first!