Last year I visited Berleburg, homestead of Benedikte (and her deceased husband Richard). When taking part into a guided tour through the open parts of the building we off course encountered several items, stories and such about Benedikte. If I understood the tour guide correct Benedikte is a upper class lady. In other words Richard could enjoy his dogs, hunting, foresting and such, while Benedikte was (and is) more regal. You could also see this distinction between the two in the portraits of them hanging in Berleburg.
I guess Mary has been "weighed" by Benedikte, according to her standards, and is considered to be way too light. I haven't seen much interaction between Benedikte and Marie, but I guess that is a bit better.
Richard called her posh and snobby in an interview once

I have zero doubt she is.