She will kill if the other person in the conflict is using lethal force against her, allies, or innocent bystanders without extenuating circumstances. She is compassionate, though not always merciful; action paid is repaid in kind, regardless of begging. Ethics and honor are intensely important personally, and even though she is a little harsh herself she can respect the strength that being merciful requires.
I've heard of TVTropes and will check it out.