What happens to Fan in the story A Christmas Carol?

As part of his voyage with the Ghost of Christmas Past, Scrooge visits several of his old haunts.  He visits his old school, where he sees himself spending some of his Christmases alone.  He later revisits a scene from his past, where his sister, Fan, comes to the school to take Ebenezer home with her.  In the scene, young Ebenezer embraces his sister warmly.  As older Scrooge watches this scene, he sadly tells the Ghost of Christmas Past that his sister died many years ago, and that his nephew, Fred (the one that invited him to the party earlier in the evening) is actually her son.  From there, Scrooge moves on to a different scene, joining Fezziwig's party already in progress.