Battling Natalie's Ghosts and Monsters

Tom here again. A short while ago I made the mistake of letting Natalie watch Ghostbusters 2. She loved the movie and kept on watching it. I went to the library and borrowed the first Ghostbusters for her to watch. She loved that too.
Recently, though, she's been afraid of monsters and ghosts. She had the problem a while before Ghostbusters, but its back again. It's quite a challenge to help her to not be afraid. Some things we've tried:

• Tell her that we've made the monsters/ghosts go away. Doesn't work so well since she reasons that they'll come back.
• Take a note from the Ghostbusters and "trap" the monsters: Have her either color or draw the monster/ghost and then have her draw a "trap" for it. She loved coloring them in and then drawing the trap. Taking it a little further, she enjoyed tearing/cutting the picture to make that monster go away. Not a good long term solution though as she thinks up another.
• Recent one, working so far: we don't let monsters in the house.  We lock the door.

Amazingly enough... that one seems to be working ok. She hasn't come up with a way the monsters can get here since we lock the door. Guess we may have to hold off on "Monsters, Inc." since she might be afraid of those monsters or come up with the idea that mean monsters don't need to come through the front door, they can just come through closets magically.