For three days, Jaina had watched, not really feeling much of anything in regards to all the violence except anger that by day two had dampened as she got more used to things.

So the fact that Johanna did that, especially when Jaina had been thinking that maybe there was more to this girl and that she could be trusted somehow, startled her more than anything else. And when Katniss started moving again and got up, Jaina's sense of relief was mixed with wondering why she'd been left alive and suddenly feeling like things were going to go very wrong.