Kaoru saying she would forgive Reiichi and Risako has been consistent with the last few chapters. Even after learning about everything that Reiichi had done, she clung to the idea that, somewhere deep inside, he cared for her in a similar fashion as she did to him. Love is a helluva drug — it can make us blind to a lot of things — and Kaoru is desperate to be loved, as highlighted by her last thoughts of the chapter.
Up until the point where she learned that Reiichi did not and could not love her, she was fighting desperately to garner his affection, and ony after Risako tells her that does she seemingly accept that their relationship is over. Whether or not Risako was honest about her thoughts, or simply using them as another manipulation tactic to drive Kaoru towards her, is up to debate, but they were certainly what Kaoru needed to hear in order to move past her one-sided love.
Which is a fancy way of saying that I hope she tries to contact Uta to begin the process of salvaging their relationship.