Going with what sandinista said about Machiavelli, you might feel like checking out
this book. It applies Machiavellian's ideas of leadership to a more modern (although business-oriented) setting. It is different from the other books out there as it is written with basic English that an 7th grader could read.
I don't think a 12 year old has natural born leadership if they are directing the way a game should be played. There was this girl named Vicky that freaking ALWAYS made me be the dog when we played house. That was definitely bossy, because she would always let Jeremiah be "dad" and they would make out behind our plastic log-cabin.