There were several Napoleons, and several Eugenies. All were part of the same family. The way to tell the difference is by what they were wearing: e.g. the first Empress Eugenie was rather flamboyant. She wore huge crinolines early, and later the big bustles. She was the height of fashion.
Younger Victoria Eugenie of Spain was the height of fashion, but “La Belle Epoque” extremely sophisticated styles more consistent of what we see royalty wear today (coming up!).
(Portrait: Eugenie of France in an 1854 crinoline)