Arianna was, in fact, just watching to try to figure out what exactly the machines were and how they worked. Obviously it involves pulling the lever, but what exactly does that do? But it's not like she wasn't planning on playing eventually, and now here's someone who can presumably help explain things for her.

"That is most generous of you, and you have my thanks. But what, pray tell, do you have in mind?"

Surely this will only lead to normal things.