Well, okay, it’s not about a “teacher” having an affair with a student, either. They are both adults. Not only did the “teacher/student” relationship end three years ago, but neither is married, so it wouldn’t be that type of an “affair” either.
Sometimes, I think people get confused about these things. The societal concerns are about people who are in a position of authority having relationships with their charges and the abuses it could foster. People like to add their own, personal issues about age differentials, but the law doesn’t prohibit that.