Buffy has only sworn off coffee so she eats lunch, but she does it quickly, not wanting to run into Alcide in the commissary. She's doing her own version of hall wandering when she spies Katniss. The scowl that (probably) gets leveled her way, doesn't bother her. She spoke to Katniss a couple of days ago and she's looking for distraction from her own thoughts. Saying hello seems like a decent distraction.

"Hey," Buffy says in greeting as she falls into step beside Katniss.