Intimate History by Geoffrey C. Ward and Ken Burns. (It must weigh about 15 pounds !)
I could find no mention of Crown Princess Martha. I read elsewhere that some biographers have her and her children living for a brief time at the White House. But they also say she lived in the Washington, DC area.
On page 384, Burns and Ward reproduce a White House log entry that shows Lucy Mercer (Rutherford) visiting FDR at the White House on June 5, 1941. She is using name"Mrs. Johnson." This is significant as it begs the question how the Princess would fit in when FDR's main love interest was back in his life.
Furthermore, on page 385, the authors disclose, during this time period, FDR changed his will to leave half of his estate for the care of Missy LeHand (his secretary) who was living at the White House having suffered a stroke.
Most agree FDR was extremely close to Miss LeHand. He also was close to his cousin Daisy Suckley. (She also is in this book.)Both of these women prove prominently in FDR's life during the period when Princess Martha was in Washington.
FDR was known to hate being alone and liked having his various lady friends around him.
Ken Burns was criticized because he did not delve into some aspects of Eleanor Roosevelt's personal life.
He replied his work did not involve tabloid gossip. He focused only on available facts and evidence.
I think reasonable people will conclude that FDR probably admired the Princess and enjoyed her company. But the record seems to show that Princess Martha's time was taken up with her war work.
She had an international reputation and profile during the war years and traveled a great deal on various missions.
Diplomatically and politically, a personal relationship with the wartime American president, was out of the question. (At least that's the way I interpret all these rumors.)
After going through this book I am convinced that Ken Burns and Ward didn't include Princess Martha for the simple reason her involvement with FDR was - on balance - not that noteworthy.
When I am on the fence about how seriously I am to take a work of biography, I look to the reputation of the authors.
Ken Burns is the recipient of 13 Emmy Awards; 2 Grammy awards, 2 Oscar nominations. He also was honored by the Academy of Television Arts & Sciences with a Lifetime Achievement Award.
Geoffrey Ward also is an acclaimed historian. He has written 17 books, three of which are on FDR.
Others have already said this, but I will say it again. These made-for-TV-documentaries are suspect. They add fictional elements to titillate the public and drive viewership and profits.
\eemed friend Trond has said, 95% fiction.