This is an interview that Myolie did with TVB a few days ago, before she left to go to China to film. She talks about her award reactions and a little about her relationship with Bosco. In every TVB interview, they mention that they've been dating for 7 years. It seems like an open secret within TVB since some of their friends had to interview and question them about their love life, even though they know the real truth all along. 7 years means that they started dating while filming the first War of In Laws?
I can only upload the first 6 minutes so go to the source to watch the full video.