I understand your concern, but I wouldn't worry too much about it- you just started this story, so it may simply be that it has a similar premise, or that it starts out in a similar fashion. That happens in this fandom- and fanfiction in general- ALL the time. I myself have a fallen angel story on this site, too (I haven't gotten it past chapter 2, but still, lol, it's here).
I would say, if you're truly concerned, post a disclaimer in your AN that you've been made aware that there is a story with a similar premise, but that you have not read it and the similarity is purely coincidental.
I'm sure as your story progresses, it will become clear that your story is your own and not a reproduction of someone elses. The main issue with bringing your own ideas to another person that you do not know is simply that, you do not know them, you have no way of telling if something you say is going to accidentally color something they're working on, of it anything they say they're thinking of working on scares you off from an amazing, but slightly alike idea you're having. And, unfortunately, you never have a way of knowing how honest a stranger is, you can approach them with the best of intentions and somehow things go completely the wrong way and you find that while trying to protect someone else from mistakenly thinking you stole their idea, then turn it around and take yours.
For the record, I have no idea what story is being referred to, or who the author is, I'm merely playing Devil's Advocate.