"Yes. Bacchus told me that, too. I imagine that being able to reject food offered by Luo Binghe to his face because it has tripped some sort of sensor might carry more weight than a more subtle protection against his magics." It might be clear, even though Lan Wangji doesn't know Susan particularly well, that she's rankling at the fact that Bacchus has dissuaded her from confronting Luo Binghe. She understands the reasoning and will respect his advice, but she's deeply displeased that giving the man a piece of her mind is off the table.