Honestly what I really wanted to do was
find a way to kill *all* the goblins without triggering automatic hostility from them (so after fighting one set you could go to the next room and they'd still think you weren't an enemy instead of plot-flagging the entire base as enemies. stealth shenanigans).
Then kill the other two leaders, Gut and the hobgoblin guy. Again without flagging myself as enemy to the entire base, so Minthara still wouldn't be hostile.
Then leverage the fact there's nobody left for Minthara to use against the grove to side with the grove without killing Minthara, or side with her except without attacking the grove if you prefer to think of it that way, and ultimately recruiting her while the tieflings and grove all survive.
Strictly speaking I have not actually tried to do this yet.
But I'm inclined to assume it's not possible, and that events would just play out as if I just took her side without the extra effort.
