I wish there was an option to remind Kahga of the tenants of their order - there is a book in the room behind her that is basically "3 easy steps to being a good druid" and one is to help those in need. Reading that should give additional dialogue options to both main druids in the sanctum. Maybe it can be used to out Kahga as a dark druid or it can be used to convince Rath that she is in the wrong and we'd help him take over. For being an evil person though, she is a little too one dimensional evil.