Elizabeth could have easily made her presence known
the last shot shows Elizabeth hapless and bound in the chamber forever (mouth gagged)
even if the mouth is gagged , nearly all human beings can produce (loud)sound though the Larynx-thorax. try it, its easy ;)
she could have gone for this , attracted attention and got herself saved rather than from rotting there for the rest of her life.
was this in the book too ? or was it the director's own 2 cents to create the shock and awe ?