I may have over reacted...
Doctor Who related trauma behind the cut...
So I have been as traumatized as everyone else by the evil sadness of Donna losing her memories of the Doctor and her life with him at the end of the last episode. (and may I add RTD you are made of evil)
She became so much more because of him, she opened her heart as well as her mind and soul during their time together. She went from screaming fishwife to made of pure awesome and it all got taken away (RTD=Evil). ....
Then I watched Left Turn. It may have taken her a while and possibly the end of civilization but she did it. She became more, everything she was with the Doctor and then some. Okay so maybe she had Rose to help her a bit alone the way but still it happened and she did it pretty much on her own. She became awesome incarnate and sacrificed herself to save everyone, without the Doctor. So despite the self involved nit wit she seemed at the end of the episode she can and will become the woman she was. The potential is there and always will be, she will become that person again some day.
That's my cannon and I'm standing by it.