Answer: A) Sluggish.
Explanation: Someone sluggish is a person that moves slow, that is lacking energy or alertness. In the given excerpt we can see that the word "lymphatic" is used to give the idea of Millie being sluggish, we can know that because of the context clue "had been brisked up a bit, by a few deftly chosen words of contempt" this conveys that she was slow and lacking energy until she "brisked up." So the correct answer is option A.