Her scowls tend to be reserved for strangers that attempt to befriend her more than anyone else. These past couple of days, drunk on the happiness provided by the drugs, she's already made the mistake of opening up to others. That's not a mistake that Katniss intends to make anymore. Everyone, herself included, is better off if she stays to herself. If she's going to accept the glitches places in her mind, then that's a part of it. She's not a good person. She's not the kind of people others should befriend.

So while she doesn't scowl at Buffy, Katniss doesn't say anything in greeting. She nods her acknowledgement as she continues to walk. But her pace doesn't change. Katniss doesn't mind the company as much as she may pretend to.