Two of Margaret Oliphant's stories include a cursed diamond ring. One of these is a supernatural story The Library Window, in which the story suggests that the ring is indeed cursed.
The other is an early novel The Days of My Life which features a deeply bitter heroine, Hester, who has learned this bitterness from her father. As he is dying he gives her a diamond ring to wear till she dies, adding mysteriously that it is "a misfortune". As she deals with the pain from a marriage which she believes is over, the ring seems to symbolize the malevolent inward forces which keep her from moving forward. (But note, Mrs Oliphant did sometimes enjoy adding a touch of the supernatural into an otherwise-realistic story, such as the sound of the ghostly horses' hooves in The Strange Story of Mr Robert Dalyell.)
The theme of a cursed diamond ring possibly came from one of the many Scottish stories and legends told to Margaret by her mother.