I have never been aware of any issues over the Duchess of Kent's background, although I can see that Princess Marina may have been a little disappointed to have had a mere baronet's daughter as her son's wife! Especially with Marina's issues with Cookie and Alice Gloucester in the past! But I am sure that after a few years, even Marina must have seen the amazing qualities Katherine possesses.
Furthermore, Katherine Kent has all but dropped the use of HRH since the early nineties, before Diana relinquished her style and precedence. To her pupils the Duchess is/was simply Mrs Kent which I think absolutely wonderful! Invariably the Duchess seems to prefer not to use her style and precedence in any situation other the grandest of official ones.
I have always had a soft spot for the Duchess of Kent, never has she complained and she has always maintained a serene dignity. Hints about the way some members of the RF reacted to her (Katherine's) illnesses left me furious for a while. I still get angry when I remember the assumptions that she was shirking her duties in the eighties. Interestingly enough though, the press always seems to have been half in love with Katherine Kent and in return for their respect of her privacy, she has been quite generous over the years, giving various interviews and continuing to be approachable, even to them. I know for a fact that Fleet street had an inkling about her teaching job, long before it was made into a story proper. It is such a shame that she couldn't have guided Diana in some way to find a niche without having to descend into a dangerous game of courting the press etc, and perhaps found another way out. I wonder sometimes at the Duchess of Kent's ingenious balancing act of discretion, loyalty and independence!!!!
Sorry I have gone off thread, but it does strike me that Katherine Kent dealt with her difficulties in a way from which Diana could have learnt so much!!!!