How 2 get sweet revenge?!??!?

Hey i really need help there is this girl ive known for a few years & shes a b*tch everything she dose is mean i cant even say how bad the things is she done & shes just i cant even think how bad well anyways i would like some advice or tips on how 2 really embarrise her or manipulate/blackmail her or make her feel really bad coz what she done is beond evil & shes like 12 or 13 plz help thx peeps ps... Im 13