There is a reason behind that. Be it for breeding, territory, food... But a sentient being killing another sentient being its not natural. At least not for Lilac.
Reason doesn't...I don't even know how to begin to respond to that non-answer. Reason doesn't invalidate the act of killing as Murder. It just...sheesh, this mindset seems more akin to an immortal or deity who just came down to the mortal plane then just an isolated faun.