I'm thinking the Avar know how to live in one type of harmony with one type of forest, maybe, and Douglass hasn't realized that's not the same thing as living in harmony with all lands.

In fact, she could have solved this by saying "Hagen was about to kill Shra. I pulled on his ankle to distract him, and he fell on his knife and died."

Which would also have the benefit of giving Barsarbe's "wanton violence always results in heartbreak" line a sensible context, as she could use it to dismiss Hagen's death as the natural consequence of his actions.