Kagha's actions seem unreasonable because we don't know her motives yet. But she was trying to achieve something on behalf of shadow's druids .
Her chest is behind the attached library behind the shelves. There is a letter to her there that says to go to the tree. You go, read it, confront her. Win some rolls and she roughly tells you her motives. Win some more, she joins you, accepts punishment. Classic "how did I become so blind" storyline that you helped her see the wrongness of her ways.
