I wonder if there are sounds, either too high, or too low, for us lowly humans to hear...that she's picking up on?? Who knows - maybe there are sounds that are causing her pain?? Try not using the surround sound system as an experiment - and see if that makes a difference?
The other thought is that she's picking up on vibrations from the subwoofer - and that's spooking her??
And one last thought: maybe she picks up on your fear/apprehension during perilous scenes in movies? My late Aussie, at times, would stand and snarl at the TV screen if something was "scaring" the grandkids....LOL!!