[Erica Sadun, Pam Korda]
Read the following references:
[TSR: 1, Seeds of Shadow, 29-30]: Elaida thinks about how Rand al'Thor must be stopped from causing trouble in Andor, since Andor and its royalty are the key to defeating the DO. She believes that defeating the DO is a desirable goal.
[TFOH: Prologue, The First Sparks Fall, 13-21] and [TFOH: 19, Memories, 260]: Elaida is pretty clearly a dupe.
From the Elaida-Alviarin interactions in LOC, ACOS, and TPOD, it is obvious that Elaida is not BA, since Alviarin has to resort to blackmail to control Elaida. If Elaida was BA, Alviarin, head of the Black Ajah, would just tell her what to do.
We receive further confirmation in TGS when Egwene is reviewing Verin's notes on the Black Ajah:
And Elaida's name wasn't on the list either. There was a notation at the end explaining that Verin had looked very closely at Elaida, searching for proof that she was Black. But comments by Black sisters led her to believe strongly that Elaida was not herself Black. Just an unstable woman who was sometimes as frustrating to the Black as she was to the rest of the Tower.
[TGS 39: A Visit from Verin Sedai]