My guess is that the imported files are still on the hard drive. If she is working in iMovie, check the movies folder. Also, in FCP, those files can be placed anywhere; it is up to the user. You can check FCP preferences to see where she has those capture and render files going.
From the Finder, you can also just look for any files over 1GB. That's likely to point to the files causing the issue. Finder > File menu > Find, then tweak the search parameters to suit you.