I have a different take on what may happen. I think Song NaHee is in for a very rough time. She and the director are a terrible match. They are too much alike, in ways that will cause conflict. He will be nowhere near as tolerant of being humiliated by having his medical opinion contradicted publicly, nor of her ignoring his wishes and she may even see his reasonable requests as more nagging. I think cracks will form in their relationship that will ultimately drive them apart. At the same time, I expect Yoon Gyu-Jin is a generally happier person and is more likely to become happier as he gains distance from the relationship and learns to accept her being with the director. We have seen moments of that when he played with the boy. If he begins to seem like the old self she fell in love with, it could lead to a lot of regret on Na-Hee’s part,
For things to resolve she has to see her cold personality as a part of the problem. The director may be a catalyst for that, as well as seeing her ex become happier out of the relationship. He needs to learn to communicate and if she begins to suspect she was a contributor to their unhappiness, it could drive her further away from him (as she thinks she is bad for him.) If that happens, he may be the only one to get her past that, and that may teach him to communicate better. Just a theory, but we have a lot of stuff yet to happen and often where things seem to be going is not where they end up.
For things to resolve she has to see her cold personality as a part of the problem. The director may be a catalyst for that, as well as seeing her ex become happier out of the relationship. He needs to learn to communicate and if she begins to suspect she was a contributor to their unhappiness, it could drive her further away from him (as she thinks she is bad for him.) If that happens, he may be the only one to get her past that, and that may teach him to communicate better. Just a theory, but we have a lot of stuff yet to happen and often where things seem to be going is not where they end up.