Adolescent book from 1980s: Girl and her lovely sister move to New England; the sister gets cancer and dies. They meet and interact with all kinds of characters, including a pregnant couple they think is not really married and a photographer. At the end of the book, she goes to an exhibit called Faces of New England and sees her own face among the portraits submitted by the photographer friend, and sees herself in a new way. Beautifully written, a book that stayed with me a long time as a teenager.
Thanks for your help!