Ronja aka Lady Amy is topfit, no fat, only muscles, but her slaves are the opposite, little flabby no muscles and so on.
The need a lesson!!!
And because she loves the power of inflicting pain... the name says it all, the two will not forget it.
She has the both on the floor, steps on them and does various workout moves.
She finds out that her steps leave nice imprints of her shoes... so the other slave needs also imprints... deeper immprints.
Or, who say's a (human) stepper is only for to stepping on... why not jumps... are making more noise and more fun for her (and pain for the two victims).