InDesign Files Eating Up Drive Space

I am supporting a Mac user that is using InDesign to create Marketing materials for our products. She keeps all of the old ads because the images etc are used again later on. From how she explained it, when she creates a new ad that uses images that were used previously, the program creates a project or package folder for that add, and copies the images into that folder. The end result is that she has multiple duplicates of the same image files (upwards of 50 at times). Her share is using up nearly half of one of our servers when it comes to disk size. It there a way to clean this up without damaging the projects? And, is there another way to be doing this so that the files are not duplicated over and over again? Thanks