If you would, post a screen shot of the "links" panel, with the info panel expanded. Make sure the image in question is selected, so that the Actual PPI and Effective PPI can be seen. It sounds like you may have scaled the image up in InDesign, thus reducing the Effective PPI to a low-res quality.
To post your screen shot, reply to this thread, and click on the camera icon in the toolbar of the reply window. This will allow you to select your screen shot to post.
Perhaps your coworker has not actually updated the links or is not using High Quality Display performance?