I am watching West Wing 1x18 "Six Meetings Before Lunch." During this episode Zoey is eating lunch with a friend and doing homework, and that friend looked eerily familiar to me. It took me about thirty seconds of staring at the still to realize that she was Valerie, Sabrina's best friend from the second season of Sabrina, the Teenage Witch.
IMDb comfirms; the actor's name is
Lindsay Sloane.
As it's been something like 6 or 7 years since I've seen StTW, I think I ought to get some snaps for recognition.