I think you can still get her by resolving Kagah's quest then ignoring the conflict. You still miss out on Halsin, but you haven't committed genocide either
Aaaaand the tieflings die because of your inaction. And you miss on the story. And XP. And loot.
The Tieflings die being ambushed on the road, same as if you'd killed the leaders of the goblins. Except the leaders aren't dead, and you can recruit Minthara at Moonrise
