So I found out that Jess' book was written by Mary Cassanova (Also wrote the book for Cecile) and I emailed her. While her response was naturally tight-lipped, I think there are a couple of well chosen words to give us some good news about her as definitely being a doll. Here's the response, and my original email:

Hi Dee,

I wish I could tell you all about what's coming. All I can say it "wait
and see." I did some incredible hands-on research for JESS and loved
the
process of finding her story. When January rolls around, I'll be free to
discuss the whole project more freely.

Thank you for your interest!

Mary


> Hi Mary,
>
> I noticed that you are listed as the author of an American Girl Book
title
> Jess: Girl of the Year. I was wondering if this book corresponds to a
new
> American Girl doll, and if so, what is her story about?
>
> Thank you,
>
> Dee

The choice words I gleaned from her are "loved the process of finding her story." To me this means they probably came up with the doll first, and asked her to comeup with the story. What does everyone else think?