Zemaille is one of the Atha'an Miere and is tall and slim with a dark face, straight black hair and black tattoos on her hands.
Zemaille is 69 years old. In fact, she was born in the year 931 NE; she went to the Tower in 960 NE claiming she was eighteen. After spending ten years as novice and ten as Accepted she was raised to the shawl in the year 980 NE.
She was an Accepted in the White Tower during the Aiel War and when Gitara Moroso had her Foretelling about the Dragon Reborn. Moiraine suspects that she was, for some reason, deliberately holding back, which she was. She took care not to learn too quickly in order to avoid notice.
Zemaille is described relatively weak in the One Power. This is almost confirmed by "The Wheel of Time Companion" where her strength is described at level 25(13), a high-middling level.
She has remained loyal to the White Tower during the split.