When I upgraded to El Cap I installed (drag & drop) the version of iTunes I was running in Snowy, so as far as I can see your friend should be able to revert her version of iTunes similarly...without resorting to nuke & pave (because iTunes doesn't sink its hooks into OS X like some other apps do), but...
  1. She'll need a source from which she can extract (using Pacifist if necessary) an older version of iTunes, with which she'll probably be stuck.
  2. Her current iTunes Music Library won't run with the older version of iTunes, so she'll have to reimport all of her music.
Edit: If your friend has got her Mac backed up she should be able to use the version of iTunes in the backup's /Apps folder, and she should also be able to import whatever she needs from ~/Library/iTunes, her original "iTunes Music Library" in particular.

Afterthought: She maaay find her original iTunes Music Library in her current iTunes folder, and although it will have been renamed, it can be reverted.

Last edited by artie505; 03/05/16 08:59 PM.
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