He made her unlikable and completely beholden to Tim on every level. Her skills were the same as Harper and Tim, genius hacker. And she spent half of his run on Tec absent from the book because Tim was absent. Even the debut story Batman Eternal gave her nothing as they were too busy setting up Harper for Bluebird.
I dont think sales are a factor, Tec is a flagship Bat book so it was never in real danger due to that alone.