I say that all of them are victims. Everything is because of the empress mother. Cheating ex didn't even want the emperor position nor loved the FL ever since. He's been listening to his mother. Mistress is well, mistress. She was even thoroughly used by the mother which completely ruined her reputation more. ML was supposedly killed and robbed off his CP position. And FL was practically kidnapped by the royals on a very young age and was not allowed to meet her family. She was thoroughly used hence her desire to escape. With these points, it has a potential for a very nice plot.
However, I find it disappointing how the romance was handled. She wanted divorce to be free. And then this mfckr trapped her again as the empress. You like her, she likes you. Why do you need to manipulate her? Impatient much? I fully support FLs father and brother for beating him. He should've been beaten more fr.
How can you be so cute and so badass at the same time? ε=ε=(ノ≧∇≦)ノ