You don't though. The druids and tieflings kill each other under a few circumstances and the goblins just clean up after. Din't have to kill anyone to get Minthara recruited.
However it is still exclusive to having Halsin, Wyll, and Karlach as party members, which is certainly a tradeoff.
So... even a 'good' version where you recruit her isn't insane. Not to mention the circumstances of recruiting her are compatible since it involves mind wiping.
But I do love how she takes zero fucking responsibility for anything up to that point because it makes her a much more interesting character than your average villain redemption arc.
Now you do have to agree to some genocide to bang the drow lady, but that's a separate issue.