Okay so she's actually stupid talented as well and the MC is a really good teacher for her BECAUSE of his parents not teaching him common sense. Those two are actually perfect for each other. Any other disciple would be unable to even come close to keeping up with his crazy standards (from his own parents training) and any other master would treat her too much like a normal person and wouldn't bring out her full potential. Oh God, I just realized that when these two grow up they're gonna become the MC's parents X 10000000. I can't imagine how much stronger they'll get with the MC thinking he's got slow growth. At the very least the world should be safe as long as those two are around (unless they destroy it themselves by accident).