Oh wow, this was quite the episode. I would expect this type of development in the last few episodes. But in the middle of the season? Unexpected, and pleasantly surprised!
All Henriette/Arsene wants to do is play Phantom Thief vs Detective with Milky Holmes. No one else makes her enjoy and feel the thrill of the game as much as they do. But Milky Holmes have recently been very useless, a lot more than usual. Hoping they would get their toys back and recall their occupation, Henriette/Arsene kept hoping that day would eventually come.
But now she has lost hope.
She snapped. And declared she would destroy the Academy. Just because. And she did. She defeated everyone there, including her henchmen who tried to stop her. And now, she will leave Yokohama. Holy shet.
I like Milky Holmes because it’s stupid. It’s dumb. But I like it. And with a sudden plot development, well, I like it even more. Can’t wait to see what happens!
Open Your Mind 
You’re definitely contradicting yourself with this anime here o.o