Responses
that's the problem with being dependent/falling inlove (not sure if she's really inlove with dowun though), your actions would lean more on emotions rather than logic. and as far as the story shows, fl literally only has dowun's family's support so she can't just "break their engagement". they're even already planning on killing her because she's showing signs of not being controlled easily, what more if she breaks her engagement? she has no one else to support her.
you provide a rather simplified solution to a rather complicated situation
The FL needs to get her shit together, if she doesn't want Dowun anymore then she can break their engagement, she still has her own allies that were not fostered by the Yang clan. She has the knowledge and power so if she fucking wants to stop she can, she's irritating me cause she knows Dowuns personality she knows she shouldn't expect anything romantic from him so she should make that decision herself unless it truly is that she hasn't learned anything at all and Dowun is the one who's actually doing shit which means if she doesn't want him anymore she should start to consolidate her influence and shit