Check to make sure she doesn't have any search filters set. If there's text put into search filters, and they don't match anything, Aperture won't show anything.
Once you've eliminated that, do you know if she had referenced or managed files in her Aperture library? If her library was managed, try right-clicking on the library, and select "Show Package Contents". Navigate through, but don't alter anything you see in the resulting file listing. From there, do you see anything in the "Masters" folder?
You may need to try repairing or rebuilding the database of the library. This article has this and other troubleshooting steps.