Mike Carey wrote:

"I did originally plan to bring Rachel back, Papercut, and I had a role mapped out for her - but by the time I came to start work on the monthly I'd had some other ideas, and most of what she was slated to do and to be was given to Elaine instead.

Which doesn't rule out her popping in again at some point, even if only as a grace note on the margins of a story."