HEY! I was just logging on to point out that same thing!
My best guess, based on the most common injuries of the period, would have been a farming accident, an accident with a kitchen knife, or perhaps an amputation for an infection.
In the context of the story, it seems most likely that the Cantor bit her during one of his frequent rages.
"If you don't know the answer -change the question."
In the reprinted programme available with the DVD, it stated that Miss Besserer was an expert fencer. Probably she had a fencing accident. By the way bok, I wholeheartedly agree with you about what might have happened in the context of the story!