In the end I believe that Sean was the reincarnation of Anna's husband. I believe he was acting out his true feelings, that he loved Anna. Once he found out he had a lover he also realized how much he would hurt the woman he truly loved and stepped back out of the picture.
If he wanted to be with his mistress he would have been...but he did not make that move.
I think Anna was in great emotional pain on her wedding day...she was still deeply in love with her former husband and could not move past that. I do not think she ever will.