Who is Atiaran from Lord Foul's Bane and what is their importance?

Atiaran Trell-mate is Lena's mother. She forgives Thomas for raping her daughter, but she cannot forgive him when he turns his back on the people from the ur-viles. As Atiaran leave Thomas, she tells him that she has a knife.... a knife she carried with the intent of killing him. In the end, however, she tells him that she has mastered her rage and simply walks away.