Yeah, there are definitely better places for that Mary Sue bumper sticker than on Twilight. I would say Princess Cadance*, but then again for the Changeling invasion to get as far as it did Cadance had to be overcome/tricked so that could count as a "fail" on her part.



There's also the question of Sunset Shimmer. If we're to believe she was Twilight's predecessor, then Cadance was almost certainly involved with her as well (even though the movie only has "present-day" Cadance and the comic tie-in doesn't seem to involve Cadance at all). Did Cadance try to be the "cool big sis" for Sunset as well and get rebuffed? Did Sunset hate her because she was already an alicorn? Did Cadance try (and fail) to pull Sunset back from "the dark side"? Was Cadance going into the fillysitting business an attempt to make up for the loss of Sunset and the fact she couldn't "save" her?



I think those are all fair questions to ask, particularly as we know the mirror portal made at least one move (from Canterlot to the Crystal Palace). That begs the question of WHY did Celestia let Cadance take that mirror with her when Cadance became the Crystal Empire ruler instead of just leaving it well enough alone in Canterlot?** If there wasn't any emotional connection at all, then Cadance wouldn't have wanted to take it with her or tried to convince Celestia it wouldn't be worth the risk of moving it.



*(Fancy "real name"? Check. Stunningly beautiful and pink? Check. A stunning voice? Check. Well adjusted/not a big jerkass? Check. Powerful? Double check.)

**It could've been lost or broken in transit, amongst other things.