Zemaille is one of the Atha'an Miere and is tall and slim with a very dark complexion, straight black hair and black tattoos on her slender, graceful hands. She moved very gracefully, almost as if dancing, but seemed shy and reserved.
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.
When she went to Tar Valon, she, like the other Sea Folk sisters, kept to herself. All the Sea Folk sisters became Browns and lived on the top level of the Library. Like the others, Zemaille never put a foot wrong, abandoned all her Sea Folk jewelry and stayed away from the sea.
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.
She is the first to greet Alviarin Freidhen, when she returns to the Tower after a month's absence.  Alviarin considers questioning and killing her, but decides not to as she notices the other Sea Folk sisters nearby.