My co-worker feels I offended her?

Talk to your boss about the problem and exactly what happened and what she is doing as a result. If you are peers (you are not her boss), you actually did her a favor by showing her the correct way to perform a task. If she's taking it the wrong way and making your life miserable as a result, you need to let you boss know so he or she can let her know that her behavior isn't acceptable.