Why I think Trollope's Dr Thorn is headed for a sad ending

Trollope's Dr Thorne could have a happy ending - Mary Thorne born out of wedlock w/ no title and with no dowry could inherit a fortune and marry Frank, and Frank could marry the love of his life, Mary, and in defiance of his snobbish and narcissistic family and find that - surprise to all - he has married into wealth - but I don't think we're headed that way, something will go wrong, the inheritance is too shaky and open to challenge and, more important, the principal characters, Mary and Frank, are likely to become victims of their own personalities, their strengths becoming a weakness: Mary so scrupulous about giving Frank the opportunity to break the engagement that she finally may have almost pushed him to do so, Frank himself so easily pushed around by his mother and by the Lady Arabella that he might agree to yet another mean proposal like waiting five years before the marriage or maybe - he's not the brightest chap around - his mother might tell him that Mary wants to end the relationship and he could be dim enough to believe her. Their big problem is that everything is so mediated - they are in love and have been in love over the course of their whole lives, but they hardly ever actually speak to each other, almost all their communication is through intermediaries and by letter. Forster famously said "only connect," and that could be an epigraph for this novel as well - if they could just spend time together and talk to each other their love would prosper, but I think that by keeping such a distance and relying so much on go-betweens and listening so intently to the opinion of others they have managed to attenuate whatever love they had.