A fine job indeed. Minerva is so real here. She's had so many excellent turns in this fest; each one is different, and yet each is in character, in its way. The same is true here -- her wryness, her self-awareness, her flaws and limits, her strengths and abilities, all so much more complex and interesting than in canon, and yet compliant, too.
I like the repeated passages, the interweaving of past and present, the way you add layers to canon (Minerva thinking of herself as a coward relates interestingly to her last word to Snape). The scene with Riddle and the rats in the dungeon is effectively eerie and revealing; I can so easily see her having a flirtation (of sorts) not only with Tom but also with dark power (today, imperiusing rats, tomorrow. . .)
Other things I like:
--Sprout and Sinistra (aww; I'm touched by that) --MM's sense that Potter's life will be an anti-climax now --the rat Melchisidec (Isn't that the name of the rat in "A Little Princess"? Nice touch.) --MM's line -- "that isn't what I meant at all" -- a deliberate Prufrock reference? So much of this story is about people not being able to hear what others mean. . .and then, so nicely in the end, hearing so well. --the perceptive, so-believable description of the aftermath of the Stunners episode --the Whitman title