In the Gathering Storm, we find out more about Verin Mathwin's background, an in particular that she
is a member of the Black Ajah (at least according to her, against her will.)
It seems like this would require her to to an active role in some of the events going on before and during the series. It seems unlikely that she could be a "passive" participant without causing problems for herself.
Do we have any information about exactly what kinds of things Verin did off-screen during the series?