I watched MEDIUM while cooking my dinner. The dreams were interesting, and the villain she was facing unique (all to the good), but I thought her resolution with the demon was just too pat, too easy. I didn't feel satisfied at the end.
And that, to my way of thinking, is more of the "reality" of such situations that DR Jennifer didn't feel it had.
I looked at it this way: The "demon" was a very specific entity. It may or may not have limitations on how often it can do its miserable deeds, but there are documented cases of people committing heinous acts who claimed to have been instructed by voices. Believe or do not believe.
In this show, Allison had a very specific dream about a specific girl and she felt she was supposed to help that girl. She had no power to destroy the demon or to prevent it from moving on, but she gambled that she could save the girl from the possession. She picked her battleground, so to speak, and fought the conflict she was equipped to fight.
Just as in life, we often tackle that which we are equipped to handle and live to fight another problem on another day.
It wasn't all pat and rosy at the end...but that seems more real to me.