You're missing a point. Killing those orcs is valid option for Sabia because that's how the society she lives in work. If Sabia was caught she wouldn't suffer consequences because she killed those orcs. She'd suffer consequences because she was incompetent and got caught."Kill one man, and you are a murderer. Kill millions of men, and you are a conqueror. Kill them all, and you are a god."
It's not a might makes right situation, it means having power in society which Sab doesn't, she is just a common murderer in this case.
Nobody cares about those orcs she killed (not even the shaman who insisted on investigation!) because they're seen is incompetent for allowing themselves to get killed... which you can see from all those orcs being surprised that there is an investigation into those orcs disappearance.