COMPOSITION
Potentially, I think the composition of this shot is very strong, but there are a couple of minor things you could do to help it. One is to move the horizontal bookshelf down a bit. This would allow the vertical shape of the books to be a little more continuous, yet broken by horizontal lines. Also, I would place the "window" in the upper right or left hand corners. Ideally, I think the lower left or right would be more effective, but that may be a logistical nightmare depending on how tall your model is and how high the shelves were! By changing the location of the window, it may also force the viewer to look more for the "waldo."
TECHNIQUE
The focus is awesome. The books are in focus, as is the model's eye. The colors of the books also make a nice picture, though I am wondering what it may have looked like in black and white!
OVERALL EFFECT
You have met the challenge, though the "waldo" may be a bit obvious, but sometimes obvious is better to many of the voters at dpc. Nice work, and good luck in future challenges.
Challenge met, even though it's not too hard to spot her behind the books. Engineering, huh? Your focus, and colors and technical aspects and all are fine for this shot. I know this is just a guidance and not a must, and sometimes meant to be broken, but personally I would prefer if the eye wan't place smackbang in the center of the photo. That way, that's really all you look at, if it was off-center, I think the viewer would "browse" the photo more, take in the different book titles, etc, more.