Makes me wonder if the master wanted the poor girl for himself. Being a young boy, Frederick probably wouldn’t have been privy to that kind of encounter.
I too wondered if the master was jealous? In most such situations, I would expect the object of fury to be the male and that he would be sold off in a far away market. That he apparently suffered no mistreatment makes me wonder if he was the object of the masters lusts and the master was furious at the woman for "spoiling" his favorite boy?
All other explanations I could think of involved fantasies unfulfilled due to repression and/or ED.