If they are really a legit couple, how Shao Rong assumed, then this mission would take a very huge leap. From the two main targets, one would be eliminated.
But, is it really that easy to eliminate a target? No. So what if they are a real couple. There could be an affair involved in the middle. If they are a true couple, then what would be the reason to hide their relationship?
This is an entertainment industry after all. Shao Rong surely heard of casting couches and such other weird relations. But their micro expressions do not show any such vulgarity. That doesn't mean that Shao Rong would confirm that they are a oh so loved couple.
Everyone around are actors and they could portray anything that any other normal human could not do. She cannot trust her eyes easily. Though she could observe everything just from a glance, she is not arrogant enough to think that everything she sees or assumes is a hundred percent true story.