"Everything I did up until now is a response to what you did. It is also a defense mechanism because why would I be the idiot who allows my equally leeching mother-in-law to steal from my house? You won't get arrested if you're not greedy."
Again, Mary had no way to debate Kate because everything Kate said was true. It was also partly Mary's fault for thinking she could get much more.
"I already admitted everything, Kate. What else do you want?" Mary said. "I'm sorry that I blackmailed you, and I'm sorry that I wanted to steal things from your home. Why don't you drop the charge now? Surely you don't want an old lady like me to be thrown into jail, right?"
"Drop the charge? Of course not," Kate refused lightly.
"YOU—!!"
"But don't worry, Mary," Kate said. "I think your offense is not that big. Besides, you haven't sold anything from my house, right?"
Do you think Kate is cunning or brilliant?
Or maybe both? ;)