As said in the chapter, Cayena now knows that the duke hates physical contact, that's why, in this life, she's given up on him and decided to respect his boundaries, especially because she needs to be on his good side, since she needs a favour from him.
Now, for Raphael, her sudden change is really important not because "uwu now that you ignore me, I suddenly love you", but because her apologising and trying to respect his boundaries is very important for him. The old Cayena harassed him and clung to him, and claimed to love him while never caring for his needs and for his comfort, she was selfish and he resented her, because he really couldn't do anything to stop her, beyond trying to avoid her.
Now she apologised and seems to be suspiciously aware of his boundaries. Instead of trying to force him, she's showing goodwill towards his needs and his comfort.
And that's incredibly important to him, because nobody has ever cared about it, or accepted it.
Cayena, being aware, but not forcing him to change or resenting him, makes him feel accepted and like someone actually cares about him. So, he'll become obsessed now...oh how obsessed he will be😏
Finding someone who understands you and accepts you while still respecting you is rare and precious, and that's why Cayena will become the most precious person to him.