It would be interesting if the reflected spell didn't kill Bella, but did kill Bellatrix. That would be unique.
Decent story, by the way. I rated you up on originality. I would suggest, however, that you get a beta to go over your work before you post it. A good beta can help with spelling, word choice, formatting, and all the rest of the little things that make the difference between an OK fic and an excellent one.
Max