Evelyn is the founding empress of the empire, acknowledged and beloved by the people from the start.
Her occupation within the Silverstar Pack is also an established one; the Luna.
It was another reason why people respected her—because she stood beside the emperor, who dominated the continent, facing several high-ranking Supernatural races and came out on top. Naturally, her power within the empire was established.
On the contrary, Empress Morgana isn't the founding empress.
She is also not beloved by the people due to her new face, and has only recently been acknowledged as the empress. And she has no power within the empire. She's not a part of an inner circle, and the nobles are also not fully on board with her.
Compared to Evelyn, she's nothing more than a decoration, than an empress.
Both are separated by leagues in terms of influence within their own respective empires.
