Help me to take revenge from my ex- best frnd?

hey guyzz i need help!!!i considerd a grl my best frnd bt tht grl used to talk nd complain abt me behind my back..she ws so cheap tht she ven used to talk bad thngs abt my family...nw i ned to take my revenge..i want to make her lfy hell...i cant frgive her easily..plz tell me wht to do..