Joan Collins hypocrisy
The whole film she's imploring Jim to give up the chase of the men, even tho they were criminals to be hanged and shot up the posse and murdered the old man (yes, he was evil but it's still murder).
Only when she discovers the rape of Emma does she go on this shrieking, vengeful rage..."Kill them!! Kill them all, Jim!! Kill Kill Kill."
It was ok for her to let them go for murdering men, but molest a woman and she wants the death penalty.