Crap, I forgot about that flashback rule! And I had a brain-fart on what mitosis was. Since all the men-folk in her life are dead (Except for zombieboyfriend who can't help anyway) and Kakashi is occupied, less chance of her being saved by an outside party, more chance of proving she's Hokage for a reason!

I will be convinced Sakura knows it, if/until the series ends without her using it. And there's physical or verbal rules that explain why she hasn't used it yet, like going up against an enemy she knows she can't win against. (I'm still working on headcanon for that fight that doesn't make me :| because I can't get past Naruto saving her)

HEART CHAKRA!