knock out two (three actually--Millicent would have had to have been taken care of)

Millicent left for Xmas, I thought? Hermione was going to say she (Millicent) had changed her mind (interestingly, the Trio have gone from assuming Crabbe and Goyle to be "bodyguards" and "goons", to having faith that Malfoy is so close to both them and indeed, all his housemates (Millicent being a random selection who accidentally got hair on Hermione) that he'll tell "his best friends" anything.)