Hi Daniel,
Nice idea, using the whatever-it-is as a frame. It's also a nice conversion to mono with a good range of tones. I would maybe have liked to have seen this with her moving a whole rectangle to the right (her left) and you stepping a step to the right (her left) so that the frame-within-a-frame thing takes up more than just 2/3 of the image. It feels a little awkward as is*. The loose thumb might have been better gripping the bar(?) as that also looks a little awkward*. There's an interesting (in a good way) tilt to the head, and the eyes are open (not squinting) and the expression is... expressive... and not blank like some of these 'through the window' portraits. The whole thing looks soft to me, which could be down to uploading issues (all my stuff looks "soft when it isn't" on Flickr)
The bar down the right hand side is not straight and the angled gap upsets my... tidyness.... The space to the left of the image doesn't add anything*, which is why I though everyone should take a step to the right.
These are all minor things though. All in all, it's a really nice portrait. Just a few minor compositional & posing tweaks really. Also - I wish it was sharper.
*in my humble opinion - take what you like & ignore the rest!