Sally wasn't turned into a demon, she was possessed.

I always wondered where that first demon went on the TV when it came out and attacked Sally. I then realized that perhaps it exited the TV as merely an apparition, a spirit, and when it attacked Sally it was actually possessing her. Thus when Sally walks out, she is simply possessed by the demon that was in the Television.

It's always fun to try and make sense of movies that were in some places thrown together nonsensically.

Only people with money say that money doesn't matter.