You need experience in life to learn how most things work. You can also learn as you go. Everybody is different in that way. Dating prepares you for what you want or don't want in a partner. So, I don't think what Director Kang said was wrong. Maybe in a roundabout way, he was asking if Yiyoung was alright with him being his only dating experience. People do change their minds.
Perhaps she's going through a hard time. She said she doesn't speak with her parents much and the granny is sick. Mi-ok doesn't seem bad, so I want to see why she's worried about what she saw earlier.