Hi,
if you delve into history you will learn that there are lots of myths and truths that are better placed in a afternoon talkshow , than in a scientific magazine, but of course this adds flavour to the topic.
last but not least, history is made by humans and leaders are very human , too. besides .. as already mentioned .. other cultures, other civilizations, other times have very different views on certain aspects of life ..
But it is important that your teacher is also explaining you the context of these stories, not only the story
So in this case just for notification:
In catherine times mercenaries, highway robbery and war was nothing unusual - so it is easy too understand that most village dwellers saw at least one other fellow in life who had sex with the next cow or horse or whatever was female and available - mostly soldiers and such people .
So it is easy too understand how such myths can dwell very fast if it is known that the queen had more than one lover in her life. If she is so keen on young officers, village people would think, then she is also keen on the next stallion - nowadays nobody would think that Bill Clinton is penetrating cows in his freetime, but on the other hand nobody is doing this public anymore in the western countries and in these .. more peaceful .. times)