That made sense if the Ober family had a blood relationship with the Frei royal family. Actually, Erica, the wife of the first Marquis Chester and Ober's biological mother, was the late emperor Cassius.
If I were the villainess, I would be the best one there is. I won't stoop so low like how that stupid Nadia did. Seriously, she does everything so cheaply. Like she really kidnapped and tried to torture Estelle just because she's obsessed with the crown prince. Aren't they cousins?