Catherine the Great had lots of lovers, many younger than herself. She behaved very much the way any male absolute monarch behaves, but it's somehow more controversial when a woman does it - and so her enemies came up with the horse story to smear her.
And the notion that women don't crave sexual variety or younger lovers as much as men is still in circulation in the form of the theories of evolutionary psychology, which is the direct descendent of sociobiology. The founder of sociobiology, E. O. Wilsom claimed that polygyny (one man, multiple wives) was genetic. The anthropologist Marvin Harris addresses that idea in his "Cultural Materialism: The Struggle for a Science of Culture":
Sexually adventurous women are severely punished in male-dominated cultures. Wherever women have enjoyed independent wealth and power, however, they have sought to fulfill themselves sexually with multiple mates with no less vigor than males in comparable situations. I cannot imagine a weaker instances of genetic programming than the polygyny of Homo sapiens.
Nobody could stop Catherine from having her affairs, but they got revenge by inventing far-fetched stories about her, no doubt for refusing to behave as a "real" woman should.
No, no horse stories for me - the story I have in mind is when one of C.T. Great's ladies-in-waiting, Countess Praskovya Bruce bagged the Empress's current favorite, Ivan Rimsky-Korsakov, which lead to Bruce's dismissal. Wikipedia claims that Rimsky-Korsakov was an ancestor of the composer, but I haven't found any other source for this claim yet.
I'm currently reading Catherine the Great: Love, Sex, and Power as research.
And now for something completely different... well, not exactly...
That wasn't a Hunnalizer, it was an Alexander the Greatalizer!