Two-Part Invention: The Story of a Marriage by Madeleine L'Engle. Actually any of her writings--there are many beyond the well-known children's books. Anyways, Two-Part Invention is her story of when her husband was diagnosed with cancer, through his treatment and death. Lots of spiritual ponderings that she dealt with. While this story is somewhat opposite of your friend in that she is the one who is ill, I think it could be very helpful and emotionally healing.