Teramina is an Aes Sedai of the Green Ajah.
History
She has been an Aes Sedai for years and is very weak in the One Power.
Activities
She disappears from the White Tower after Egwene al'Vere becomes Amyrlin Seat and asks all Aes Sedai to re-swear the Three Oaths on the Oath Rod. This would put strong suspicion on her being Black Ajah.
Egwene thought Teramina might have been posing Mesaana, but she had been in the White Tower for years.
Another possibility is that she was taken damane after the Seanchan raid.