My own "River Theory"
My wild theories are circling around Bernice Summerfield. It doesn't work with the "I've never seen you so young" quote but it's as good as anything.
In case you're not familiar with Benny...
http://tardis.wikia.com/wiki/Bernice_Summerfield
Paraphrased by me ....
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Bernice Surprise "Benny" Summerfield was a 26th century archaeologist, a companion of the Seventh and Eighth Doctors, and an associate of Irving Braxiatel. An adventurer in her own right, both before and after her years in the TARDIS, Bernice was destined to make choices that would decide the fate of the universe and to become worshiped, in some cultures, as a minor goddess of inebriation.
Benny's Diary: Bernice kept a diary since she was a child. (BNA: Oh No It Isn't!) She wrote, longhand, in a notebook that she kept with her at all times--if she forgot, she would often attempt to go back for it. (NA:Falls the Shadow) Benny frequently "corrected" diary entries (via sticky notes, correcting fluid, or crossing out the old entry) after they were written. (NA: Human Nature) She published at least one compilation of her diary entries. (BFBS: The Doomsday Manuscript)
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Interestingly enough, Moffat has used her a little in the story "Continuity Errors." This story is the semi-basis for "A Christmas Carol." Seven goes back and re-writes a character's past in order to manipulate a future event. Seven is more sinister in the novelizations and his interference always has darker, callous, undertones.
As to the "younger" quote ... perhaps it is a relative appearance thing. She hasn't commented on Eleven's apparent physical age. We do know she's living out of sequence with the Doctor.
*shrugs* Who knows ... and, yes, I do realize that Seven and Eight have met her but we do know the Doctor's memory is crap. Eight had a horrible time remembering the past and Nine was so traumatized he didn't want to remember the past.
Just a theory ....
In case you're not familiar with Benny...
http://tardis.wikia.com/wiki/Bernice_Summerfield
Paraphrased by me ....
***************
Bernice Surprise "Benny" Summerfield was a 26th century archaeologist, a companion of the Seventh and Eighth Doctors, and an associate of Irving Braxiatel. An adventurer in her own right, both before and after her years in the TARDIS, Bernice was destined to make choices that would decide the fate of the universe and to become worshiped, in some cultures, as a minor goddess of inebriation.
Benny's Diary: Bernice kept a diary since she was a child. (BNA: Oh No It Isn't!) She wrote, longhand, in a notebook that she kept with her at all times--if she forgot, she would often attempt to go back for it. (NA:Falls the Shadow) Benny frequently "corrected" diary entries (via sticky notes, correcting fluid, or crossing out the old entry) after they were written. (NA: Human Nature) She published at least one compilation of her diary entries. (BFBS: The Doomsday Manuscript)
***********
Interestingly enough, Moffat has used her a little in the story "Continuity Errors." This story is the semi-basis for "A Christmas Carol." Seven goes back and re-writes a character's past in order to manipulate a future event. Seven is more sinister in the novelizations and his interference always has darker, callous, undertones.
As to the "younger" quote ... perhaps it is a relative appearance thing. She hasn't commented on Eleven's apparent physical age. We do know she's living out of sequence with the Doctor.
*shrugs* Who knows ... and, yes, I do realize that Seven and Eight have met her but we do know the Doctor's memory is crap. Eight had a horrible time remembering the past and Nine was so traumatized he didn't want to remember the past.
Just a theory ....