Love doesn't always last forever. And sometimes it can crumble so spectacularly that you never want to see or speak to the other person again.
Celestia was perfectly content with that. But when Twilight Sparkle suddenly appears at the palace in Canterlot, after a century of silence, she has no choice but to talk to her.
Politely, of course. Always politely.
*Credit and many thanks go to littlerobotbird for the concept and editing of the cover art. As near as I can tell, the original picture is Jykinturah's work, but the source post seems to be gone.*