No clever answers, so I will take a stab.
I take it she then saved each document, with the original name? Ummm, from the backup? - I assume you already eliminated that possibility!
If there is an an older version with the references, but multiple changes in the current document, you can unformat the backup, do a compare documents, and keep the new text and keep the references, but running thru the document and accepting or rejecting the appropriate information.
Depending on the length of each document, another way is to replace the parentheses with curley brackets and remove all the ", et al"s (if it is in that kind of format) and then run endnote. It will mean sorting thru duplicates of the author year matches, but that is easier than reinserting each reference.
Finally if it is a long document and in a numbered format, the easiest way I have found to cope, is to create a new library dragging the references into it, in the numbered order (so the number matches the record number) or putting the number in the “label” field, if it isn’t used, Then editing the numbers to have curley brackets around them with the # in front of the number (for record number matches), or editing the preferences for in text citation to use the label field.
Best of luck.