He is referring to this:
Sly: Are you coming for Thanksgiving? Are you coming for Christmas?
Primo: No, I don’t think so.
Days later, an email from Sly:
Sly: I had written another email but decided not to send it.* We will feel abandoned if you don't come for Christmas.
* That is not passive aggressive AT ALL. Either send the email or don’t send the email, but if you don’t send it, what’s the point of mentioning it other than to imply that it was so awful that it could not be sent?
Me: Yeah, but if I have your mom say it, it makes her character more unlikeable.
Primo: My dad would never say that.
Me: The problem is that I need to have a happy ending, which means redeeming your mom, which means the reader needs to be able to like her. The reader doesn't have to love her and it's OK for your mom to start out unlikeable, but then we have to show her to be likeable underneath it all.
Me: If I actually ascribe to your mother everything she actually said, readers will not like her at all. So I have to put some of the mean things she said and did on your dad.
Primo [the engineer]: But my dad would NEVER say "We will feel abandoned." He would never say that he had written an email and decided not to send it.
Me: This is fiction.