One of Them by Kitty Zeldis
At Vassar in 1946, Anne Bishop hides that she is Jewish because she doesn't want to be socially ostracized. She develops a friendship with another Jewish girl, Delia, in secret. Delia is unabashedly herself and doesn't care that she has no friends at the university. At times, Anne, is in awe of how self-confident Delia is. One day Anne betrays Delia and their bond is fractured.