The rest are probably hanging out with the two girls in Hermione's dorm we never saw :-D
The class list isn't totally reliable, since she changed her mind later in an interview or later draft which got scrapped and gave Dean one magical parent. But it lists Hannah Abbott as Muggleborn (although apparently she later became halfblood too, probably so Jo could kill her mom), Wayne Hopkins and Megan Jones as halfbloods, and Sally-Ann Perks is unmarked. Weirdly, the Harry Potter wiki lists Katie Bell's friend Leanne as being in this year in Hufflepuff; I don't know where they got that information. (The movies also have the names Luca Carruse and Alice Tolipan on the Dumbledore's Army list, and there's an unnamed Hufflepuff girl who must have a twin sister in Gryffindor because the actress played a Gryffindor too, but who knows whether this came out of more of Jo's shoebox of notes or whether the moviemakers just made it up.) Zacharias Smith was there seventh year, so he must not be Muggleborn unless Jo forgot (I can't find any other indication). There's also several names on the list with no House affiliations or blood status. So who knows what the "real" situation is there. I think there's enough wiggle room to make Terri's idea work.
no subject
The class list isn't totally reliable, since she changed her mind later in an interview or later draft which got scrapped and gave Dean one magical parent. But it lists Hannah Abbott as Muggleborn (although apparently she later became halfblood too, probably so Jo could kill her mom), Wayne Hopkins and Megan Jones as halfbloods, and Sally-Ann Perks is unmarked. Weirdly, the Harry Potter wiki lists Katie Bell's friend Leanne as being in this year in Hufflepuff; I don't know where they got that information. (The movies also have the names Luca Carruse and Alice Tolipan on the Dumbledore's Army list, and there's an unnamed Hufflepuff girl who must have a twin sister in Gryffindor because the actress played a Gryffindor too, but who knows whether this came out of more of Jo's shoebox of notes or whether the moviemakers just made it up.) Zacharias Smith was there seventh year, so he must not be Muggleborn unless Jo forgot (I can't find any other indication). There's also several names on the list with no House affiliations or blood status. So who knows what the "real" situation is there. I think there's enough wiggle room to make Terri's idea work.