It's because she already knows Perez will become the emperor and she wants to be the Matriarch and can't become the empress. Family is first for Tia though she really love Perez.
Of course Perez knowing that he's really crazy in love with Tia with defy the empire's law in order to be with her.
This might me a spoiler so if you don't want to know more please skip my answer
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I saw in some comments in tik tok from people who read the novel and they say that the prince will change the law for her, so she can be an empress and a matriarche at the same time
i read the novel! (spoiler)
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yes that’s true! however the law cannot be changed if it benefits the current emperor so perez threatened the current emperor (jovannes(?)) to change the law before perez ascends the throne so the law is applicable for the future emperor and empress (tia and perez ^-^)
AWWW THATS SO ADOROBLE
Damnnn Perez is a MAN, every one needs a perez in their life
funny how tia thinks she can't do anything and perez will still end up with ramona even after changing the trajectory of basically everything