Oh, I don't doubt that Donna may have felt a twinge of maternal grief over Seth's murder, but I really wouldn't read more than that into her statement. It was an off the cuff remark.
I very much agree with you that her mention of Seth Rich was more of a warning shot across the Clinton's bow.
“Oh, I don’t doubt that Donna may have felt a twinge of maternal grief over Seth’s murder...”
I agree. And Seth was such a young fellow, only 27 yrs. old. I can see her using the term “child” when speaking of his death.