Yeah, Kit's got a kind of anime sailor suit going on. Poe does too, actually, but like Dongs pointed out she has a long skirt on rather than a short pleated one (also Poe is wearing long sleeves).
It might seem odd that they would wear those kinds of things since they look so anime, but I did some research on clothing and sailor-suit style outfits did exist in the U.S around the late 1800s/early 1900s. Though I think they were designed for much younger girls (I didn't kill myself doing research, I just googled some pictures and found a site and ....there ya go).
So, I guess I'm somewhat historically accurate but not perfect. Ah well!
Girls having access to sailor schoolgirl outfits and pleated skirts makes me think of some kind of Wild West Sailor Moon combo...
The Dreadful being unconcerned with accuracy makes all sorts o' things possible.