Maybe you don’t know some background info for Mr. Chen.
He was married when Milk tea admired him. I think he did properly when he refused the hug. He had to consider his wife and kid’s feeling when he accepted her hug in public. His refusing her, I saw a very responsible man since he was not able to promise a future to her. If he left some room for her, then things would go bad to both his family and Milk Tea. He is not selfish but he is responsible and you may not know what’s in his mind by being that cold. They just met in a wrong time and he was completely not available to a decent lady. His cold might just a kind of love that he wanted her to have a better life. After all, they are teach and student. His love to her is a decent love from a great teacher.
Milk Tea was single at that time and she should not love a man who had a family in the first place. A broken marriage would hurt another woman and their kids.