Shakespeare's Dark Lady sonnets, and the unknown woman that they are addressed to. Scholars trying to identify her have variously suggested Mary Fitton, Emilia Lanier, Marie Mountjoy, Luce Morgan, and several others, but no persuasive evidence exists. More recently the term has been used to describe any unknown muse.
Beatrice di Folco Portinari (1266 - 1290), was the muse of the poet Dante Alighieri. She appeared as a character in two of his works - La Vita Nuova and the Divine Comedy. She was married to another man, and Dante met her just twice, but his feelings for her were powerful enough to be carried throughout his life.
White Nights is an 1848 short story by Russian writer Fyodor Dostoevsky (best known for his novels Crime and Punishment, and The Brothers Karamazov).
Henry James (1843 - 1916), possibly now best known for his ghost story The Turn of the Screw, did indeed write a novel called The Reverberator: a comedy that details the results of nasty but true stories, about a Parisian family, being printed in the newspaper of the novel's title.
Gretchen is a character from Goethe's Faust. She drowns her illegitimate child. Hetty Sorrel is a character from George Eliot's novel Adam Bede. Pregnant and unmarried, she delivers the baby alone and then abandons it in a field to die. In Wordsworth's poem The Thorn, Martha is abandoned by her betrothed, who marries another woman. Martha, pregnant and mad, is frequently seen on a hill calling 'oh misery!'. Her baby disappears: 'some will say/She hanged her baby on the tree;/Some say she drowned it in the pond'.