If she knew that an article about her relationship will be published than she didn't really have a choice but say it herself. It probably wasn't her plan to reveal it at all that time but anyway, I love how she did it. Standing there during such a big event and simply saying that she's getting married. In front of everyone even though everyone knew about the dating ban. It feels like she's saying to the industry: "No contract can't keep us from falling in love and wanting to be happy with our beloved one."
Like Trekkie, I also can't really believe that she would have been allowed to stay. Or they told her "If you break up with him, you can stay." I'm not super familiar with jpop-groups but I've heard a lot about the dating ban and the consequences and it would be strange if she was allowed to stay, I think.