Sorry but the way you keep saying that Shauna Hoare was the main instigator in this is wrong. Im not saying she wasnt jealous of Becky, she probably was, but thats not the reason for this horrific crime. Nathan Matthews is one dangerous, twisted individual who fantasised about this type of crime. Shauna Hoare is heavily influenced by him and whatever he says, goes. Shes obviously a damaged, sick person too otherwise she couldnt have done what she did, but you are wrong when you say she was the "master manipulator" in this.
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This was NOT a case of one "less attractive" or "dumpier" girl being eaten up with jealousy and manipulating her doting boyfriend into murdering his " prettier" step Sister!
It IS a case of a predatory sexually twisted and depraved man, manipulating his younger more impressionable girlfriend ( who was damaged enough and idolised him enough to become equally sick in the head) to go along with whatever sickening ideas his warped mind could come up with, and indulge his fantasies .
A monster created another monster and Becky lost her life because of that.