Significance of Leonara's tale

Leonora is the reclusive inhabitant of a grand house along the stage-coach route, a shallow woman who once jilted the hard-working Horatio for the frivolous Bellarmine and then was jilted in turn. The tale turning up at this point is a little strange. It just seems to be inserted in the novel. Leonara serves as a character foil to Joseph even though she really isn't prominent in the book. Horatio is perhaps the onlu positive person in Leonora's story. I suppose Lenora's story serves to flesh out other characters in the novel.