I tend to follow canon as much as possible and so far, there’s only the one book that says how Cadance became an alicorn. She became an alicorn all on her own. This didn’t change in this timeline.

Cadance ascended. And Nightmare Moon saw an opportunity to form this new alicorn into a pawn. One that can watch over the Empress’ domain during the day, ensuring her will is enforced among the diurnal ponies.

That doesn’t change her nature as the Princess of Love, though. And Shining Armor being her personal guard gives Twilight an “in.”