I've read this piece several times and each time I read it I love it more. Your language and imagery is so beautiful, and you've adapted poetic elements of language well into a prose piece. Too often I see attempts at poetic prose come off more purple and ostentatious than eloquent; you don't make that mistake.
I feel strongly that this piece could be published somewhere. There are two moments that took me out a bit, and I think looking back at them might improve it all the more.
I backtracked, stepped quietly away, but sometimes when she looks me in the eyes and asks me where the thunder's gone I wonder whether she heard me breathing behind her, then.
In the next paragraph she's dead, so in keeping with the flow, it makes more sense (to me) to have this in past tense as well, rather than switching to present tense. At any rate, it took me out a bit because I was wondering when the time was the narrator was relating, given the story preceding and following.
This I learned after her death, after that summer, when the boy came up to the funeral podium holding a battered piece of paper that held only aimless sketches of her eyes and crumpled against it.
This struck me as a little too omnipotent for your otherwise entirely human narrator. I pulled this sentence out mainly because in the sentence preceding, the narrator says he only learned this at this time. It's the detail of what the paper contained that had me wondering how he would know. How did the narrator come to pull all this together? It closes a bit too quickly, with the narrator knowing a little more than he should, and it does a disservice to the rich detail of the rest of the piece. A couple of sentences to explain how he came to know what he knew, in an organic way that flows with the rest of the story, would bring the last paragraph in line with the rest of it.
I tend to talk the most about pieces that impact me the most. You did an amazing job with this, it's a truly beautiful piece.