From what I understand, Hasbro used the spelling of "Cadence" in their early material. Now they stick with "Cadance" exclusively for all of their promotional works involving her.
That can't be right. Cadence is the proper spelling, and it means "a melodic or harmonic configuration that creates a sense of repose or resolution" in western musical theory.
Yes, "Cadence" is the proper spelling for that term. I'm aware of that and what it means. Although, Hasbro currently spells her name as "Cadance" on their merchandise.
Her name is spelled Cadence.
As seen here: [link]