"Yue Jinghua" does not remember any specific information about the Royal Xuanji Royal Academy; she does not know that Xuanji Academy is divided into an Outer Court and an Inner Court.
The Inner Court is where true elite education takes place. The students either possess astonishing talent or come from extraordinary families, and there are many who have both.
Lie Sisi is exactly the type of student that the Inner Court favors to recruit—born into a prominent family and blessed with remarkable talent, destined to be a distinguished individual among people.
As for the Outer Court, they accept people like Yue Jinghua, whose Dark Skill is a complete mess, whose family has fallen into decline, but for various reasons cannot be outright rejected by the Academy.
The matter of the Dark Pill is nothing more than an excuse by Xuanji Academy. With the Dark Pill lacking a name or an owner, how could it be determined whether or not it was acquired by Yue Jinghua herself?