IE Visiting her eyes and ears, calling on informants, visiting the bank to convert Tar Valon notes, etc.

I don't think she is a darkfriend or a Black Ajah, namely because all the evidence points to the contrary. Plus, we know she is bound by the Three Oaths and cannot lie. She is not walking around engaging in the mysterious activities - she's just keeping her activities secret. In fact, we know of most of her "off screen" time - for one, she spent a lot of time with Adeleas Namelle and Vandene Namelle to research the Forsaken, ancient history and forgotten records. It is possible that she pieced together balefire from these records, as well as the psychological profiles of the Forsaken.

Plus, it really is not hard to trace a Forsaken's movements; in terms of the overall game mechanics, they are moving on the same board as you are, but acting on a parallel set of rules. Thus she could figure out which Forsaken was in a city by a number of criteria: A) Unnatural phenomena or unlikely events that started occurring (ie: widespread nightmares in a city, a large number of leaders mysteriously changing personalities or vanishing creating power vacuums, mysterious deaths), B) timeframe when these events occurred, C) modus operandi and Talents of the Forsaken, D) "new" citizens or nobles that have appeared when A and B happened and finally E) if all the factors in A, B and D match up with C.