If anything, Finnick's reaction to his experiences with animals before he found himself here have made him more cautious, more suspicious. That's probably unsurprising since those experiences have included animals that were genetically engineered to use as weapons during the Dark Days and against the tributes in the arena. There had been plenty of animals that weren't mutts, too, but anything unusual in his experience was automatically suspect.

At least a snake was, mostly, just a snake.

Still, something in him found it a little relieving that he could protect himself, even if he didn't know just how he'd done it.

"She didn't mean to do it? It just happened?"

That does sound like what Benedict is suggesting. He can imagine it happening like that: Kelly being furious at the fight and interposing herself, and a barrier pushing them away like his had pushed at the snake.