The Wings of the Dove.

Kate is secretly betrothed to a struggling journalist, Merton Densher. But she knows her Aunt Maude will never approve of the match, since Kate's deceased mother has lost all her money in a marriage to a degenerate opium addict. When Kate meets a terminally ill American heiress named Millie traveling through Europe, she comes up with a conniving plan to have both love and wealth.