Because, as early as the first few encounters, Qiu Tu noticed something was amiss.
Princess Xi seemed to be concerned about King Kang, trying to find ways to help him, but... her intentions didn't seem so "pure."
For example, she would always mention how despicable the Kou family was, how they held sway over the court, how they harbored treacherous intentions. (Chapter 492)
For example, whether facing Ai Li or Qiu Tu, the first thing she expressed was her indictment of the Kou family, rather than concern for King Kang's safety. (Chapter 499)
Actually... this doesn't align with a normal woman's mindset.
A woman who truly loves her husband, when her husband is critically ill, would she be more concerned about "neighbors" or "relatives" seizing the family assets?
No. They would be more concerned about their husband's wellbeing.
After stalling things, the top priority would definitely be to deal with her husband's illness first.
