As of Hotfix 10, there is no way to keep them both in the same playthrough without mods. The KO method has been patched out afaik, you can only do it with the Sheepthara exploit. There is a datamine from Patch 4 which hints at a new possible way to recruit Minthara in a future update, but the devnote indicates it would still be at the expense of the tieflings. Consider sending Larian your feedback if you think this particular aspect is a dealbreaker, it would be a shame if you bought the game but never played it again.
Oh wow I didn't know Sheepthara method was a real thing. This would actually solve my problem and the whole absurdity of the method might be just what I need to enjoy the game again.
I'll dust off my monitor, get myself from level 5 to level 7 and give this a shot. I'll make sure I disable auto-updates for now too in case Larian patch it out.
Big thumbs up, thanks.
