Turns out Rarity's talents don't end at fashion and generosity. Well that cutie mark never really made sense anyway…

When Twilight finally manages to create a stable and efficient time travel spell, she is surprised to find Rarity can cast it quite easily. She encourages Rarity not to use the spell, but hey… wouldn't you?

So of course several time wimey shenanigans later rarity has managed to bring back discords reign and pretty much break the universe, leaving a very unhappy twilight to clean up her mess.