Are there any differences between your waifu and the canon version?

[Rares]

The Nightmare Rarity events more or less happened, albeit she didn't die at the end, though she was separated from Rarity physically but was able to retain her own physical body. She believes it was because they couldn't use the Elements of Harmony on her that time.

There's something of a truce between Equestria and her faction.

She's existed longer than the princesses.

If it's okay for me to ask, just for my own curiousity's sake, what's the difference between what Nightmare Rarity is, and what she was with Rarity?