Is it possible we're being too literal with Hilgya? Are we sure there wasn't some missing context with the story about Ivan?
If the action was evil surely Durkon would have commented on it?
Killing a mook in a dungeon to achieve a party objective at the direction of your party leader surely isn't evil.
Finally, are we sure she would want to murder Durkon were he alive? Maybe it's more of a figure of speech that in her mind would lead to a reconciliation?