What I love the best about your Kingdom Hearts fic is perhaps that you can write about relationships without making them romantic, or rather, their could be romantic implications, but you don't beat them into the reader's skull with a mallet. If I choose to see Namine's longing for Sora as a romantic one then I can, but if I prefer to see it as a kind of envy of the human relationship that he shares with Kari that works as well. I like the fact that you aren't afraid to employ a little ambiguity. You give the reader enough credit to work things out for him/herself.
Some people have rated this piece for ambiance and I think that's very well deone on their part. There is so much to be found in this story. Your descriptions are lovely and dream-like and you have inserted such wonderful nuances into certain parts of the story.
For instance, this: "No, he wouldn't have even thought of it. Not even in his heart's memories. But with just a little bit of tweaking..." Where it begins to seem that Namine is dreaming about Sora and changing his responses just a little to suit her own desires.
Then Namine herself admits that Sora is dreaming this scene, that she's inside of his dream somehow. But finally Namine's thought that she isn't sure who is the dreamer and who is the dream is quite lovely and ambiguous. I enjoy the fact that you don't provide a ready answer to exactly what is happening. That works well with the theme of dreams which are always vague and uncertain.
The fact is that I love Namine and I think you have done an excellent job of writing a wistful little piece from her perspective.