The Villainess is a Marionette

Cayena, the Imperial Princess, was known as the most beautiful woman in the Empire. She was a woman who knew nothing but evil and luxury.
However, she was destined for ruin: she would be used as a chess piece by her younger brother to secure his throne and killed by her crazy husband.

“I’ll make you the Emperor.”
“… Sister, are you referring to me?”
“In exchange, give me freedom.”

She had to change things before she became that Cayena.