Katniss doesn't care if anyone stops her or not. Haymitch probably needs the drink to get through this explanation and at least the alcohol in the Nexus is good quality and not likely to destroy his gut in one swallow.

She gets a bottle of whiskey and a glass, plunking them down on the table in front of him. "Have a drink and let me start explaining. Don't get drunk, though. I need you to focus."