She knew that Yan Sihan would not consider her as someone who would rebel or usurp the throne, after all, what did she have? She was just a "simple-minded" young girl.
There's even less need to mention Prince An.
Rebellion required soldiers and money, and amongst these, money was most important.
She did have some money, but could she gather soldiers under Yan Sihan's watchful eyes? Even if she had the guts, she didn't have the ability.
That's why she had no intention of rebelling at all.
Usurping the throne was a different matter, though. Prince An was a member of the royal family, and she knew he was not an ordinary man, otherwise, she wouldn't have used him.
From the very beginning, when Prince An came to borrow books, he had ulterior motives.
No matter what Prince An's intentions were, both parties had their needs met. If the usurpation went smoothly, they would also leave their names in the history.
It all depended on how the usurpation was carried out.