Why was Cecilia doing all this to torment her father?
Simple: revenge.
If Cecilia had genuinely wanted to introduce Arthur to her family in a proper manner, she wouldn't have orchestrated something this outrageous. She might have been bold, but she wasn't reckless. No, this was all carefully calculated chaos—a way to needle her father in the most infuriating way possible.
Cecilia knew exactly how maddening this situation was for Quinn. An audacious boyfriend, spending the night with his daughter, now casually dining with the family and boldly navigating the undercurrents of imperial formality—it was a perfect storm of aggravation. And Cecilia was reveling in it.
That wasn't to say she didn't also want Arthur to get along with her family. Marriage was in their future, after all, and it would be awkward to hate your in-laws. But this particular meeting wasn't about diplomacy. This was about teaching her father a lesson.