Such strong and plausible characterizations, of Petunia and Millicent, of course, and of Dudley and Vince, too. (I love that Dudley has gone into business with Piers.) You do such a nice job of fleshing out this world with spot-on details -- Sooty, the wonderful notion of Petunia catching the Knight Bus with a wooden dowel (and keeping in touch with Hestia), the relationship between Millicent and her father. You show the difficulties of Muggle/magic pairings very believably.
Her eyes as she studies Millicent, though, are the opposite of prey Fascinating Petunia detail.
"Harry Potter? Your cousin is Harry sodding Potter?!" Poor Millicent! I can just imagine how she feels.