Nene doesn't really love Kou, I think. What she loves is herself. She's a narcissist.
I think she's a misunderstood teen girl who's been told constantly not to show emotion or smile because she's somehow "better" by not being herself--whereas she got to constantly see Amane, the person she was probably closest to, be praised for being awesome and attractive and all that by being "allowed" to be her (albeit exuberant) self. And it gave her a complex. And was probably too much for her to handle, so she tried to create distance, but was stymied by how desperate Amane was to keep her in her life, and probably by her own miasma of contradictory feelings. "I love this person, but it also hurts to be with this person".
Now she's found a cute little camera girl who tells her how great she is when she's just herself. That her smile is OKAY, and even desirable. I can see why her behavior is weird, and why she's pursuing Kou. Even the nasty "look at me" display in the cafe; it was just that. "Look at me, I am accepted for myself now too, you're not the only one. Can you please finally let go of me?"
But I'm probably thinking too deeply about it. Thanks, insomnia!