Wow, this is excellent, just excellent. I love it. I've wanted good Minerva/Umbridge fic forever. I've tried (and failed) to write it myself, but now I don't need to.
I love well-written second-person, and you've done a stellar job with the form. Your Dolores is perfect -- distanced from herself, filled with desire and anger that are essentially one and the same. Her back-story makes such good sense, as does the well-handled cat motif. And of course Dolores is the sort who would want to be equally "well-liked" and "well-feared."
My only regret is that there's only 1000 words of this fine fic; when a story is this good, I'm greedy enough to wish for many times that number. Thank you!