She is a tall, dark-haired woman, who likes to wear her hair in a coil of braids atop her head. It is unknown whether she and Viria are identical twins.
Being a Sitter in the Hall means that Raechin is also a high ranking sister and a strong channeler by Aes Sedai standards. Thus she had the strength needed to travel.
Raechin became a Sitter in the Hall of the Tower after the White Tower Schism was mended. Egwene al'Vere considers her an odd choice for the position, but not unexpected. The Sitters try to hold a secret meeting without Egwene, discussing ways temper the Amyrlin's power when a declaration of war is called. Raechin voted for a proposal that would allow only Egwene to deal with the monarchy of the world, which includes Rand al'Thor as he is King of Illian, while the Hall would take over prosecution of the war and deal with Gareth Bryne's army. In that same meeting, Raechin voted in favor of the new rules and procedures in the Hall, which included temporarily replacing a Sitter when she is absent from the Hall and that no meeting of the Hall can commence without all Sitters and the Amyrlin Seat being present.