I don't know about power gaming - suspect you mean meta-game. But if you do, it's not such a stretch really.
For starters, there are tons of clues leading up to meeting Minthara suggesting she's something special; the drow corpse clues, drow disguises working well, goblin adulation of drow (and her specifically), her role in the 3 as the more proactive leader, the clarity of her mindlink cutscene, Moonrise dialogues, and her suggestive language/behaviour.
Sure, each by itself is minor, but together indicates something on par to recruiting Halsin.
And if you play paladin MC's, you're prudently hotkeying nonlethal and optionally leaving a trail of unconscious anyhow.
One thing I don't like are the answers you can choose to give her about why you spared her life and not Gut's or Ragzlin's. You can't say along the lines of 'You were my enemy, but I liked your style.' At least, I don't remember a similar option.
Then again, there are lots of enemies (goblins especially) that don't deserve to be finished off. They got character. Minthara's got a lot more.
