Hi @Lucia-S
You will always get the error as this is the expected behavior of SharePoint that if you are updating some content and at the mean time it has been updated by some other user before you do the update. What's more, the newly created page is actually the last draft version of the page that is empty when it is copied to SharePoint Designer 2013. So, there may be some error when your colleague saved the page. Actually, she has failed to save it and the page is still in an edit mode now.
You could tell her to save the draft again and open the version history of this page, then restore the old version through the versions.
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