I mean Minha is just stupid, but Seungho is the biggest asshole in this situation, he betrays her premeditatedly, he lies all the time (just to satisfy his ego), she in return lies, cheat on him? (it hasn't been confirmed in 100%) and works in a bar as hostess to make money for both of them... as I wrote earlier: she is foolish, he is an asshole.
All in all, this is just a pornhwa and there is no need to get too involved in psychoanalysis xD but also from here I feel that MC's life will become VERY tough and complicated.