Spoiler!
Well, Inseo asked her whether she likes his mom and asked why does she live with her husband. He basically said her that she likes his mother so why marry and live with him and that he's curious why she is not with someone she likes. He also said that he knew this because her eyes is like his eyes when he sees yi hyeok. So this made her divorce her husband. And this made Inseo guilty because he was the reason for her realisation.