The biggest problem I see with this picture is her eyes. The edge of her glasses cyut right through her eyes, distorting the eye balls, very awakward and unfalttering. This is obviously a posed shot. You should have noticed this and have her adjust her glasses accordingly.
On the topic of glasses, the light reflection off her glasses is very annoying.
Other things - messy hair, oily face especially the forehead, these are things you can control.
Somehow, how the pen is resting on her chin does not look natural to me.
The composition has that posed look. I believe your intention is to capture her in a moment of deep thought. So, even if it's posed, it must not come across as being posed.
This may sound weird, but try having the pen in her mouth...know what I mean?
Other than that, listen to DP...It may even look nice in Black and White. I am a clean freak, so the spot on the wall is really distracting to me... I kept wiping my lap top thinking it was me, but it's not...Other than that, I like the paneling of the wall, and it goes well with your theme- simple, clean, smart.
This photo was actually sort of spontaneous, even though it looks posed. We were spectating at a competition, and I sort of caught her in that position. That's also the reason why we could not pose properly.