There's a site called keepvid.com where you input the url of the youtube video. You can use that to dl the video. If she uses Safari on a Mac, you can avoid keepvid altogether and find the link to the file in the Activity monitor.

If you're loading a video from youtube while monitoring activity, you'll see that one item being downloaded is larger than the others. That's your video. Copy the link to that item in the activity monitor and paste it into your navigation bar and it should download the video as "get_video." You'll want to change the name to *.flv. These files are playable in vlc and other media players.

The Video Download plugin for Firefox also does the trick.

or this: http://vixy.net/

there's also this online video converter where you just type in the youtube url and it does everything for you (i think).