Here Haymitch uses the importance of Katniss' appearance as an argument for why the new Head Peacekeeper should stop beating her. The way Haymitch explains it, it doesn't matter what Katniss has done or not done to deserve a beating. What matters is her presence at "a photo shoot next week" where she has to look the part "modeling wedding dresses." Of course, Haymitch is using appearances as an excuse to save Katniss, but in a way, her life does depend on her looking the part.