I'm guessing that Dexter's Dad went to her when he was young for advice on how to handle a sociopath / psychopath? She is one of the foremost experts after all. Perhaps she was the architect of 'the code', or at least a part of its conception? If so, will be interesting to see how Dexter reacts to her. Over the past few series he's started to develop a resentment towards his father for putting him on this path - at least at times.
but the problem is they have a central character that gets away with far too much with no consequences and we have had 7 seasons of it already...and now were expected to believe that this top dog super psycho hunter wants Dexter on her side instead of simply shutting him down? come on....its a little ridiculous for a final season.
Why dont they just focus on Deb and Dex relationship for the season and make it as authentic and as gritty as they can, leading to some massive showdown...they dont need these side stories thrown in at this stage of the show (which basically amount to villain of the week/season) since all the characters have massive back stories that they can use.