Who is Nynaeve al'Meara from Winter's Heart and what is their importance?

Nynaeve al'Meara is the mighty Aes Sedai, who will help Rand to cleanse the male side of the Power in the climax of the story. She remians close to him, but she is aghast at his non-traditional antics, such as bonding with three women at once. While cleansing the Power, Nynaeve is stunned by how horrible the male side is. She cannot understand how Rand could tolerate his side of the Power.