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If I were needing to share a single device with someone and keep it pretty simple, i think I would try:
1- Create a new collection [Daughter]
2- Copy tune. [in the main library, long press song then 'copy song', upper right.]
     a- Re-name the title from 'Song 1' to 'Song 1 - a123' [and Song 2 to 'Song 2 - a123', etc], to allow searching in 'all fields'. Keeping the tag unique [ie., 'a123' or  'D copy',] and only used to refer to one person. Only the tag needs to be searched for. It's possible to use one of the other searchable fields for id-ing song differences/owners, but it would add another step or level of complexity.
     b- Select the collection for the new song [Daughter], and removing it from other folders or setlists/collections, etc., as needed.

I currently do something similar to this when I'm experimenting on a tune in the app.