Well one thing I know for sure is that you have to bag everything that her head has touched like her pillow because there is probably lice on her pillow and it could spread. So bag it and then tie the bag shut so that the lice die. Your sister also needs to get that shampoo that kills the lice. She probably should go to the doctor to be safe. =)
Get the RID from the store for your sister. In the meantime do not lay on her pillow or share her brush. I would have your sister sit in only one chair in the living room or family room and put a towel down on that chair. You can pick the towel up and wash it and if no one else sits there they won't pick up any of the little critters.
DON'T GET NEAR HER! to get rid of it, just get lice shampoo but to avoid it yourself, as I said, don't get near her, change your bed sheets and pillow case, don't let your laundry or hairbrushes get mixed up, if you have any pets with fur make sure they don't get it either. hope this helps