Even then, even in the very beginning, Donna was able to recognize the blurring of the line where Harvey ended and she began, that they no longer existed as two separate entities.

Gosh just so poetic and beautiful when it comes to these two. Not just because of their history but that fierce loyalty is so present in every thing they do. 

You captured it all so perfectly that this is my canon now. Everything from Harvey's mother and brother to that old picture he still has, Donna's almost engagement, and "the other time." And that phrase you have in there about how she smells like "pencils and perfume", that's so perfect that I wanna cry. Great work.