
spoilers
she breaks off from the magic spell cast on her by cerdina since childhood. it feeds on her loyalty to the crown, which makes her nauseous and gives her frequent headaches. a kurkan magician helps reverse the curse slowly. it's a pretty painful process for her but the ML is very patient and doesn't force her treatment. they even get separated twice, one by kidnapping and the other by her choice, because she wants to know how and why she got that way.

It helps weaken the curses. One time doesn't break it. So that is why they have to do it multiple times
Plus, Cerdina didn't need to use very strong curses the first time but she soon realized that her control getting weaker, and uses much more stronger curses later on.
However, the hardest part of the curses is that it prays on Leah morals and the difficult part was figuring out which part is her thoughts or manipulation of the queen. So Leah feels attracted to Ishakan, but is resistant to it. It can be mix of her actual thoughts and the control of the queen. Considering that a political marriage with Ishakan is far better prospect than that trash of a fiancee.
I need someone to give me major spoilers from the novel how does she escape the royal family and end up with him