Came to suggest the very same thing, except I heard that she was 4 y/o when her father dies in the fire, and he's been in the sanitarium 7 years, making her eleven. Now, perhaps tack on a year here or there for Karloff to run around and she's like 13 y/o, maybe 14--i.e. underage for marriage and needing parental consent--but that actress didn't seem to me to be 14 y/o.
Excuse, please, I notice later on in the movie that when they seek the photo of Karloff's character they reference the fire being in the year 1923. If the film is from 1936, tack on 12 + 4 and you get 16 y/o, which conceivably was then and there under the age of consent to marry.