Such a ridiculous retcon.
She literally gathered up all the monsters in the forest and sent them on the warpath toward the nearest human settlement. An action that, barring the interference of some truly absurd deus ex machina (like MC), would absolutely result in many, many human casualties. Yet we're expected to believe that she wasn't willing to kill the guy she found snooping around?
Even if we accept that as true, what was her plan exactly? After the horde of monsters razed his city to the ground, she would let him out of the cage and say "Now that we have formed an irreconcilable death grudge, cya around lolol"