That didn't surprise her. If he was giving her a knife, and acting like that with Katniss...it probably was something Katniss knew about, or at least he would have known how she felt about it. Though Prim didn't think she could bring herself to use a knife on a person (or, for that matter, an animal) unless she was cutting to help them, she would carry a knife around if it made her sister feel better.

Katniss had been here for over a year. Back home, Prim had thought that her sister had feelings for Peeta - at least, that had been what she'd read from Katniss' actions, and she'd never pressed the subject. This wasn't home. And more than that, Katniss was the important one, here, and there. As long as she was happy, as long as something was making her happy - Prim could accept whatever or whomever that was without complaint.

Though later on she might not be the happiest of people in regards to Sokka.

This wasn't later, though, and Prim grinned, just a little. "How long have you been seeing him? How did you meet? In the woods hunting?"