This is fantastic! Jadis' narrative voice is spot on, and I love how you tied her to the various plots and problems that appear in Narnia (as per your comment above regarding what Jadis may or may not have been up to all those years). And the linguistic angle was particularly effective -- I'm reminded a bit of Guy Gavriel Kay's Tigana, which is all about the magic of names and forgotten language. Lewis' Narnia is oddly one-note, especially compared to Tolkein, and Aslan's overarching power does explain that very well.

And the Lady of the Green Kirtle was just a bonus! I've found her fascinating since my first encounter with The Silver Chair, and I love the idea that Jadis created her to be a companion and spy.