
Something that isn’t really addressed in “It takes a village” is that, while Agatha dresses pretty much like she does in canon while she’s in Mechanicsburg, she has a radically different fashion sense in Beetleburg, where she decided that in order to pass herself as a Very Normal Student, Nothing To See Here, she simply had to crib Vanamonde’s fashion sense.
Possibly that’s just because the mental image she has for ‘respectable young adult’ is Van, and a general unawareness of the fact that, no… Van is… he’s just a fancy goth. Also these are not her colors.
But also, because she tends towards dark and cool colors, it gives her a much more matronly vibe that does help when it comes to keeping the other students in line.
Later, after they find out she’s a Heterodyne, many of the people who knew her at TPU will think ‘oh, that explains why she always dressed so creepy’, but no. No, that was just her plan for blending in. That was Agatha trying to be subtle.