If the black-haired guy in the cover is the demon king and if she will become friendly with him in this life then I will stop reading this.
I get that everyone has to take a side and I don't think the demon king is wrong for how he treated her since her and her people were probably doing the same or worse to demons but that cannot be overwritten. Regardless of whose fault it is, that happened to her and she should not associate herself with anyone like that.
Also, aside from her sister, I hope she isn't trying to be close to her asshole brothers in this life time. I get that she lacked a specific talent in a family known for that exact thing but they abandoned her so she should just live for herself especially since she spent her past life being a doormat