What was the point of the ending?

per previous thread/poster:

I believe that Jesse won in the end.The Demon consumed her flesh but her spirit lives forever.Jesse knew that in order to save her soul from the Demon she must sacrifice her body.The Demon was afraid of Jesse.She represented Hope and Innocence.The Demon tried to possess her spirit but the demon failed.So the devil consumed her body but her innocent soul lives forever.That's how I see the end of the movie.

It made me think of the idiom dog eat dog world or survival of the fittest. Gigi couldn't handle what she had done and Sarah had no qualms with it.