I have a Percy Jackson guessing game, but this one is for The Kane Chronicles.
Her yellow eyes look tense when she's about to kill.
From having to fight an enemy for years on end,
She's finally glad to get some fresh air.
If you're her target, she'll hunt you down.
Doesn't matter if you're a rodent or not.
Two little knives are strong enough to kill or threat anything,
No matter if it's the guy at the super market not giving her a discount on Friskies,
Or a god who wants to kill the ones she protects.
Two different answers are okay, doesn't really matter =D