Well, her hat seems to say "misuti." The Pixiv tags hint at some kind of lighting error when thrown in Google Translate. A quick toying with the brightness and saturation in Gimp doesn't reveal anything like in the usual "tilt your LCD and it appears" images, though.
I asked ChaosKnight, who added the tag, and the "misuti" is what he meant. Indeed, comparing with other pics, her hat doesn't normally say that. (It's also the first three characters in her name as pronounced in Japanese -- why the "a" is missing is anyone's guess.)
