If you're looking into a protection spell or charm, there are several things you can do. Probably one of the easiest options would be to enchant an object the person wears frequently so that it will act as a protective device. There are many plants that can be used as a tincture or infusion to soak the item in. I personally prefer black snake root, but something else may appeal to you more.
Or, you can make something for them that has a protective symbol drawn into it, or etched, etc. There are many protective symbols, from many different cultures in the world. Choosing one you like best and then taking a photograph of her, drawing the symbol on the back, and keeping the photo in a safe place should do the trick.
Something else that is said to banish demonic entities are a few simple hand motions. Both of these are said to be the creations of the Ancient Greeks, but they could as easily have originated in Sumeria, Babylon, or Egypt. The first one goes like this: cross your index and middle finger and hold them in front of your chest, then thrust your hand out forward, keeping the fingers crossed. The second is this: make a fist, then extend the pinkie and index fingers out again. Hold your fist so that the fingers extend horizontally. Keep the hand in front of your chest then thrust outwards, maintaining the "bull head" shape.
Good luck in your endeavors!