People with psychological obsessions are strange; once they assert something, no matter what others say, in their worldview, they'll only acknowledge it as, "I'm right, you're all wrong."
As for something or someone they're obsessed with, they'll think, "It's mine; it can only be mine, and it can't belong to others. If I don't want it, it can only be because I don't want it; it can't be that others made me not want it, and the other party certainly can't not want me."
Cheng Su does not rule out that Chiang Qing has such a mindset. Qi Taiguo's rejection made her feel embarrassed. How could he not want someone as good as her? How could he refuse her?
So, her desire to have Qi Taiguo might just be to prove that she is right.
Later, a series of events occurred, and Chiang Qing's obsession began to deteriorate. The misfortunes that befell her were all blamed on the "source," which was, in her recognition, Qi Taiguo and herself.
