How do you tell someone who has exponentially more power and Lexi (that would be plural for Lexus) than you do that she is plagiarizing? Very, very carefully.
Option 1: Quietly credit the original sources and don’t get into a conversation about it.
Option 2: Imply that someone—probably a lowly editorial intern, who has long since starved to death in a NYC garret—neglected to add the citations that the Big Important Person wanted her to add.
Option 3: If the Emperor refuses to acknowledge that something might need to be credited to another source, bring out the big guns. Use the word plagiarism. Remind him of Doris Kearns Goodwin, who, like many college students, didn’t mean to plagiarize (or so she claims) but got fucked anyway.
Depending on your level of control of the project, Option 1 tends to be the best option. It avoids drama. And copyeditors don’t need drama. (Except me, because I need material.)
However you approach this minefield, use all your writerly powers to keep any hint that the Very Important Person is to blame for the transgression. Take a deep breath. Remove any sense of agency from your queries. Read your queries 25 times. It’ll be OK.
What options am I missing?