I think it was a drama with many episodes. The lead actrice was a daughter-in-law. I think she got divorced and she went to America. There she became a famous painter. Nobody in Korea knows this. After some years she came back to Korea and she kept it a secret  that she was a painter.  

Maybe Mama: Nothing to Fear. Though they were not married, they were just exes. And she comes back to Korea with her son, who the guy doesnt know exis