Hmm, definitely a different approach. Is it Harry -really- going nasty or just using whatever he can to survive? There is a difference and I can see where Hermione could, with effort, help him and guide him. It won't be easy for him, but she has a chance.
BTW, was that Harry's spirit working with her before she went back? That would be one explanation as to how she survived as long as she did before coming back. If so, I wonder where that spirit is now?