When you love somepony, you have to deal with everything which comes with them. Fleur is perfectly aware that she's effectively inherited Zephyr. She just doesn't understand why she isn't allowed to kill him.
Fleur de Lis moves to Ponyville, after finding Fancypants cheated on her, then got her shunned by the Canterlot elite, and slowly becomes infatuated with a certain yellow pegasus. However, she seems to have come down with hoof in mouth disease
Unable to have a child of their own, Canterlot socialites Fancy Pants and Fleur give adoption a shot. Enter Chestnut—a filly from beyond Equestria who will quite possibly turn their life upside down.
Celestia blames herself with losing Luna to the Nightmare. Now a thousand years after Celestia fled her responsibilities, a changed world will have to deal with the return of Nightmare Moon. And a reluctant Celestia will have to help.
Having realized that the duration of Discord's "reform" may exactly equal his only friend's lifespan, the palace sends Fleur to assist Fluttershy with acquiring a social life and guarantee a next generation to adore. (What could possibly go wrong?)