Who is Karin from Friend of My Youth: Stories and what is their importance?

Karin is a woman whose life has been torn apart by a bad relationship with an abusive man. Her ex-husband Brent treated her badly, did stupid things when drunk, and eventually cast her out unfairly after a religious conversion. It is also possible that he is responsible for the loss of their child, though Karin is adamant that the baby would have died anyway. She repeats this to herself several times, as if trying to convince herself that it was not her fault and that she could have done nothing to save him. This indicates the terrible guilt with which she lives every day. She tries to repress it, but a simple snow-storm is enough to drag up painful memories.