some color distortion on the hair - background is over-exposed... This isn't something I would look at and immediatly think "A", either... crossbar is iffy, for instance.
While this is a very striking image in its own right, it is somewhat contrary to the challenge, which was to find an "accidental" letter. This was clearly a staged shot. I suppose you may have been doing a shoot for some other purpose, and then "discovered" the "A" in post-processing, so I'll not be a complete hardass about this anyway.
I really like this photo - backlighting effect is great model is beautiful and the gritty door makes for a nice surrounding. Only qualms are the halo around the top of the hair caused by the light and I think you'll probaby get disqualified for the copyright symbol on the bottom left - so far as I know they aren't allowed. Still, its a good shot, so I hope no one complains about that.
A couple comments here - first, I don't think any 'people-posed' shots will do well notwithstanding the gratuitous sexy woman - these are not "Accidental". That said, if you were going to make an A, her hands should probably be behind her back - out of sight.
Lastly, I see some letters and/or symbols in the drop shadow border of the image, at least one of which may get the pic DQ'd.