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.
Encountering other girls in the sky is exciting!!! Probably none of them are as good conversationalists as Isabella but she can examine their magic and that is so cool.
"Nothing in particular, it's only that I go to a boarding school and I'm the only magical girl there so outside of a club meeting they ferried me to at a larger school I haven't met many other magical girls. And my power is that I can sense magic! Or, at least, magical girls; I have thankfully not yet had the chance to test if it registers swarms."
What a bizarre individual.
If the vulture girl seems to want to talk more she's willing to pay her social dues but will not initiate further discourse.
"Because the school felt obligated! Also, I didn't know the way, and wasn't at the time confident enough in my flying speed to gamble on being able to make it between when classes let out and when the meeting started."