Nira, known in-game simply as Woman, was a resident of Riverville. She was married to Pentas. Nira drowned herself on the sea after her husband, Pentas, was killed by the Riverville guard. She is a key character in the The Voice from the Water quest.
After Pentas was killed by the mercenary sent by Meldor Featherwall, Mathilda couldn't bear the weight, and drowned herself on the sea.
After her death, Nira placed a sort of "curse" on Mathilda Featherwall, the woman whose actions indirectly caused Pentas' death. Mathilda seems to be condemned to relive her wrongdoings, in a coma. During The Prophet's investigation of Mathilda's illness, Nira guides them around, giving them access to Pentas' house, pointing out the mercenary that killed her husband, and, finally, killing Meldor Featherwall as revenge for what he did to Pentas.
If The Prophet chose to make Meldor pay for what he has done, Nira sympathizes with them and releases Mathilda of her illness. If The Prophet chose to let Meldor go, for any reason, Nira despises what they have done, and kills Nira together with her secret lover. Either way, she seems to disappear forever, having tied up the last loose end that kept her from resting.