My headcanon how Sunset Shimmer become alicorn and co-ruler of Equestria.

🔸️This happening after Twilight coronation.

🔸️She return in Equestria, because her human counterpart stole powerfull magic scrolls.

🔸️Sunset become alicorn while fighting with her human counterpart possessed with Pony of Shadows.

🔸️After human Sunset safe rescued and return to human world, the pony Sunset return pernament Equestria.

🔸️She become seventh element of harmony, the element of emphaty.

🔸️Sunset and Starlight now live in Castle of friendship.

🔸️Later Twilight and Sunset together fight with Phantom Infinite and Dark Havok. The villains are enemies with Pillars of Equestria, Celestia and Luna.

🔸️Sunset confront Ahuizotl and angry that, he deceit his reformation and hurt Fluttershy feelings, after he reveal his true malicious intention using with staff of Sacanas.

🔸️Ahuizotl used control magic of water, but stole by King Charlatan.

🔸️In final true Grogar return and almost conquest Equestria until was stoped by now mane seven.

🔸️Mane seven defeat Grogar thanks magic of friendship.