1. If you're running the exact version your friend needs you don't need Pacifist; all you need to do is burn it from your /Apps folder to a disk, and drag & drop it from the disc to her /Apps folder (although it would probably be better to d/l v 11.4 from Apple as per freelance if that version is OK). I'd repair permissions after reinstalling.
2. You'll need to get rid of the version of iTunes.app (
only) that she's got installed now in one way or another, and it may be a pain depending on which version of OS X she's running.
3. When your friend upgraded iTunes her ~/Music/iTunes/iTunes Music Library.xml was changed to a version that's not compatible with the earlier version of iTunes you're going to (re)install, so you'll have to either recreate or reinstall the lost file:
- I believe the original of that file still exists in ~/Music/iTunes, but with a changed name, in which case you can change it back to iTunes Music Library.xml.
- If not, you'll have to reimport her entire ~/Music/iTunes/iTunes Music folder, and that will result in its being recreated.
In either event you'll want to trash the new file.
Hope that helps.