Shining and Cadence knew that raising a princess would present challenges above and beyond those of raising a born alicorn. As one might expect of Twilight Sparkle's brother and sister-in-law, they prepared as best they could for many of the problems they might encounter along the way.
Of course, that doesn't mean anypony told Flurry, who feels like this is a bit of an overreaction to her wanting a cookie that happened to belong to somepony else.
Flurry in the cover image courtesy of AleximusPrime, used with permission. Source link to the image can be found by mousing over it.