The whole Genocide thing specifically isn't her, no, but that wasn't the poster's complaint; s/he simply perceived Cheetah as a dumb mook who could never have come up with anything so elaborate or successfully headed and manipulated the Society that way (thanks, Pfefier! Way to be, Rucka!).
A workable resolution to her behavior currently, as arrlaari pointed out at noS_D, is that she's bluffing the hell out of Diana and her intention from the very beginning has been for Diana to kill Genocide. This would explain both the mustache-twirling I LIVE TO DESTROY YOU (she needs to get Diana involved enough and pissed enough to take Genny down) and the weird torture scene (she had every intention of helping Diana find Genocide, so not breaking free of the rebar and rolling over so easily becomes the sensible path). It's still a bit MWA HA HA, of course, but far closer to the Cheetah of yore than taking her at face value and assuming she's simply gone Circe.