You were just an ordinary lady walking in the streets but...you got hit by a truck, got reincarnated to another world in the novel you read, as you are the duke's wife(villain) , which basically that you are in a force marriage...you are the villain character.

You then wakes up in a unknown room and looks in the mirror who you see in the mirror is not yourself rather a beautiful lady that is not your original appearance

"Eh..? "

As you said