Problem with the ending + her remaining silent (spoiler!)
Sure, that's an ending for the ages, but it looks like Elizabeth's hands are free, and she could have easily ripped the cloth away and screamed as the three were leaving the dungeon. So...why didn't she?
I've thought about this and wondered if she knew she'd lose either way. Assuming that someone heard her screams, didn't think it was just a ghost and go to investigate, then what? She admits that she faked her death and was having an affair with the doctor? I've got to think that back then, there'd be harsh penalties for that kind of thing, especially if the adulterer was a woman. Maybe she decided that it was better to die in the dungeon than face an uncertain fate elsewhere? By revealing herself, surely she would waive any legal right she had to Nicholas' fortune, and her lover was dead.
I don't know, it's all speculation, and of course it's just a movie. But her hands were free and that gag didn't look tight!