I WAS THINKING CHINESE PEOPLE, BUT THAT WOULDN'T BE MEDIEVIL WOULD IT?
15TH OR 16TH CENTURY
I found a Russian Empress Elizaveta Romanov who lived around the 1700's, who was Peter and Catherine's daughter . She was not only promiscuous, but she did torture people she had issues with. In one instance, one of the courtiers' ladies started a conspirancy against her, so she had his tongue ripped out and sent him to Siberia.
This family had a history of brutality and promiscuity. You can read more about the history here: http://www.dailymail.co.uk/news/article-1098889/Dynasty-decadence-Behind-Romanovs-glittering-facade-lay-epic-saga-depravity-unspeakable-cruelty.html
I hope this is the information you are seeking since she falls into the criteria of promiscuity, cruelty, and torture.
NO ITS TOO LATE, IT WAS THE 15TH OR 16TH CENTURY, AND IT WAS AN EMPRESS WHO DROWN PEOPLE
Sorry I could not be of help. Please do not rate my service, since it was too late. I will have this closed since you seem to have accepted Mike's answer. Joan
NO, DIDN'T ACCEPT ANY ANSWER BECAUSE IT WAS NOT THE RIGHT TIME ZONE I WAS LOOKING FOR. THANKS ANYWAY