I've been thinking about Donna's whole role in the finale, all up to the end of Stolen Earth. In Turn Left, there's a bunch of different Donnas that I noticed.
There's the Doctor's Donna, who went in to that fortune teller's place. Her past was changed, which I think created a parallel Donna (the past one), because at the end it's still the Doctor's Donna that tells him what happened.
Rose meets the parallel past Donna, who then has to go back in time to stop her past self (which I think is another parallel Donna, cos that past self ends up meeting the Doctor and so on, while the Rose-Donna ends up dying to make sure her past self takes the left turn).
In the end it's the Doctor's Donna that tells him what happened, so either she has made up a bunch of parallel worlds and they've closed themselves up, having served their purposes, or they're all somehow going to come back to be used since that white haired girl at the Shadow Proclamation said that thing was on Donna's back.
Any speculation on that or am I just overanalysing? lol.