Did Game of Thrones foreshadow Margaery killing the High Sparrow years ago?
Basically the theory is that since now Margaery is faking being a convert of the Faith Militant that she's going to keep manipulating the High Sparrow and eventually kill him.
And people think this is because of the scene in season 4 in which her and Olenna are looking at necklaces for Joffrey's wedding and something that Margaery said about the length of Joffrey's cruelties.
SOURCE
It amuses me how far people reach for straws. The High Sparrow is Cersei's to kill.