It might be in their best interest, alliance wise to appear as enemies or to at least get all the aggression out of the way, so the fight could still be viewed as a positive thing. I assume the Capital could heal her black eye pretty quick with their savvy medical stuff. If Katniss ruined Johanna's look for the Ball, there might be hell to pay. Would I assume after the fight breaks up it would be around time for the session to be over and for them to all go back to their rooms?

Gale and Finnick and practice posing in the spotlight without their shirts...for science. Yes that. 

Oh, I probably won't get it up by then, but when you wake up, you'll probably have something.