The Mule, you mean? They do foreshadow him, but he's represented as something predictable and also different from this "pivotal woman." It's kinda a mess.
The series focuses on Seldon himself and other heroic figures doing heroic things, rather than on the idea of psychohistory working with large populations over long time scales. This may be because Asimov's Marxist-influenced interpretation of history is something they found distasteful, or it may be because the idea of replacing the entire cast every few episodes was considered commercially unviable. Either way, it's really not very Foundation once you scratch the paint off.