Gwen, was an employee at Wolfram & Hart who was charge of the firm's Files and Records, in fact she seemed to be Files and Records personified, as she had access to every file and reference in the firm. She was most likely killed by The Beast.
The fact that her eyes flickered when "thinking" and that she repeated phrases indicated that she was probably not human.
Behind the Scenes
She was portayed by Stephanie Courtney, better known as "Flo" from the Progressive Insurance advertisements.