I'd never seen a description of this personality disorder, but I'd heard bits and pieces about it, and you are surely correct: M and W do encourage each other in these tendencies. I don't have time right now to go back and reread the passages where they interact, or I would quote, but from memory, I think they do almost everything on the list, at least when they're together. As others have said, Willoughby, who, at 25, should be the more mature of the two, frequently (usually!) encourages Marianne in her immature ways. Very interesting, thanks!