"Love" and "hate" only meet, and mingle, properly when they transcend their own desires and becomes "obsession". Rika is not obsessed with Sousuke as a lover, more than one instance has showed us this( from the "dai suki da yo" in the spa bath, to her talk with Misato in the motorhome, and then last chapter). She's obsessed with the perspective that he, and only he, can give her the "true love" she so wishes: adoration. Undeniable feelings for her. And while Iwabuchi may love and care about her, Sousuke was molded to become this way to her. Carved by her for her, if you may.
The only problem with this whole process, is the sheer dramatic irony of Sousuke's ego existing.
Rika's ego is so big, that all her schemes seems to be thoroughly planned and executed as she so wishes, regardless of how, flawlessly. During chapter 61, Sousuke even addresses that, since the begining, Rika did not look at him as an equal, but merely a piece to be played with. But the contrast is that, while Sousuke's ego seems to be adjusting well his superego X ID, when Miyabi appeared to him, he looked at Rika and started strangling Miyabi to death. Even he cannot deny his impetus when push comes to shove.
And this might be just the wildcard to turn this whole scenario: Rika believing she has him 100% under her control, only for him to smash her, given the chance.