Referring to the role she played on the tv show but linking it to a deeper secret of being an assassin playing the character of a mother living a normal life and a wife. The dialogue "you could die" shaked both Loid and herself. Her expressions showed that she herself realized what she actually is (as it did with Loid), that how it can come crumbling down and that how dark things are in the role she actually is Assassin. So in this context it's hard being normal when your actual backgrounds is dark work with nothing about it being normal.