One of the things I love about this series is how it looks that the characters want to grow from their past selves.. at least in the case of Woojoo, especially considering how she was portrayed at the start. There's some things that she has to improve, sure, but steps have to be taken little by little. And that drunken confession seems like such - she doesn't really feel resentful towards Hanbyul (despite his immature actions from the present)... but she knows she hurt him before.
I kinda want to say that Hanbyul does WANT to improve as well, but... hmm... at least he does realize that he has been a jerk with Woojoo regarding her intentions with Chulho, right? He messed up and BADLY.