Abhorsen (Abhorsen, #3)

by Garth Nix

Not since Kemmeru’s illicit still had caught fire when Lirael was doing her turn on the librarians’ fire brigade. She was pleased she hadn’t forgotten the technique, and that Nick was a lot lighter than Kemmeru. Not that it was a fair comparison, as Kemmeru had insisted on being carried out with her favorite books.

I don't know anything else about Kemmeru but I desperately want to be her best friend...