It's true, she is cute! And it's a very lovely black and white portrait, with beautiful lighting and great composition. Her expression is completely natural. It's a BIG stretch to say this fits the challenge though!! I'll subtract one point for that (I'm not harsh on that kind of thing).
She is cute. Like the composition. I think it is a little overexposed - the freckles do not show up as well as they could. Meets the competition? A stretch.
Though I see no connection to the pi challenge (maybe I didn't look hard enough!), it is nevertheless an adorable shot, with great lighting and composition.
Very good portrait. Not seeing the pi reference besides the title. Great lighting, focus, DOF, and use of the black and white. If this was a portrait challenge I would give this a 7 and maybe more.
I'm sure you're receiving comments to the extent that this image does not fit the challenge, and I have to say, it's probably true. I'm pretty liberal when it comes to interpreting challenges, but I'd still like to see some kind of connection to the real pi somehow. Maybe she could be looking through a circular object, for example, or holding a hoop, or focus on her lovely eyes: something.
As for the photo itself, I think you've captured her personality well. I love the composition, and B/W works very well for this image. Crystal clear focus where it needst to be, and i also like the tones a lot.