She is sitting in the library, studying. It's her most common pastime, by hours; spending time with her sister is more enjoyable but Jaromira prefers to socialize more broadly and Katarzyna would only get in the way. This is better on net; the two of them share a room, so it isn't as though her sister's time is entirely hogged by the other girls who call this boarding school "home." Or at least "prison." Katarzyna doesn't mind it, though; the school library is excellent, and basic manners and care for the books has endeared her to the librarian to a sufficient degree to lubricate the interlibrary loans process when there's something she wants to read that they don't have.
"Oh, that makes sense."
She beams at her.
"So I bet you know what all the best stuff is."
She will gleefully show Isabella All The Best Stuff.
It is delightful!
Isabella is delightful.
So is Katarzyna!
It is a really good thing Katarzyna knows these exhibits so well. It means she can talk about them intelligently while most of her attention is focused on how excellent Isabella is.
A lovely combination. Perhaps they should hold hands while they muse.
"You're cute," accuses Isabella.
--She ducks her head and giggles. "I think I haven't been called that since I was young enough to automatically qualify."
"Well, maybe you are not usually in circumstances that cause you to show off your cute."
"That sounds entirely plausible."
"When I visit you at school no one will recognize you, you will be too cute."
"Who is this strange blonde magical girl and how did she get on campus?"
"And why did she steal Katarzyna's student ID?"
"And her outfit? And--gasp!--her girlfriend!"
"And why is the girlfriend going along with this? Oh no!"
"Clearly the most nefarious of plots."
"Why would someone impersonate you?"
"To get at Father's money, probably."
"I suppose that is the obvious thing, isn't it. Not especially cinematic."
"Trying to steal my girlfriend would be the cinematic thing."
"Then I have to spend most of the movie duped, how unfortunate."