Why is she being cold when I've done nothing wrong?

Welcome to the world of women my friend. My guess (and that is all that this is, based on past dating experiences) is that she has lost interest in you. Most woman have a hard time telling a guy this directly, so using the silent cold treatment is the main method of telling them to hit the road. I would advise leaving her alone for awhile and see what happens. If she calls you, then proceed with caution (some women love having their men like puppets on a string). If she doesn't, then write if off to experience and move on. Best of luck!