https://en.wikipedia.org/wiki/Elizabeth_Lavenza

https://frankenstein.fandom.com/wiki/Justine_Moritz

https://www.sparknotes.com/lit/frankenstein/character/william-frankenstein/

You know, I liked Del Toro's version, partly because it specifically addresses my pet peeve, that the pedants who try to correct people that "Frankenstein is the Doctor" don't realize the Monster should also be surnamed Frankenstein, but I really don't like that it has done exactly what I thought it would, trick people who can't read or who can't hold multiple canons in their head into thinking that the Monster isn't a monster.