Martin please read one of the links you posted
http://www.cherylbolen.com/kent.htm
It states "This prompted biographer Mollie Gillen to spend five years thoroughly researching the lives of Prince Edward (who became Duke of Kent) and Madame de St. Laurent. Much of this research involved the examination of countless letters and records in the Royal Archives.
"
In my opinion this is very believable, can you see if you find any information on Mollie Gillen