I agree, and I honestly think that's the reason why she hates tia and shannet (other than them being in the way of. her plans). Because unlike her they got the privilege to be recognized as the head of the house. Unlike her who had to be sold to that son of a bitch of an emperor, and watched her incompetent brother get the seat of the head just because he was born a son, even though she was definitely more qualified.
that also ties nicely with the fact that she doesn't mind (and she knows) tht her own son is growing to become incompetent. Although she pushes him to be better than Perez, she doesnt care if he's good enough to be an emperor. We initially thought she was always spoiling her son for power (he sits on the throne, glory for her and Angenas) and just becuse she is her own son. But last time, when her son confronted her, she showed that her ambition is becoming the REAL power behind the throne. Which means that the frustration at being born a woman and not being able to inherit like her own incompetent brother has made her eye the highest position of power
I think Lavini has had a grudge with having a brother or the system at the time where sons are prized and daughters are seen as property, what with her saying he became head simply by being born a son. Looking back her brother had shown being human more, with previous chapters I've read of him showing hesitation and questioning the decisions of his sister. It's just a shame that Lavini is a rotten bitch to the core..also I love saying her name, so pretty~