I almost never do opinions, but here we are!
dot: Both of them share similar energy levels and hype each other up like there's no tomorrow. She would probably fall for Dot as well once they realize how well they mesh together, even though Dot's flirting will go right over her head. Still, the two make an excellent pair and would probably funnel a ton of energy into the band.
kai: A bit put-off by his quiet demeanour at first and might pester him until he opens up. She'll do everything to see him smile, which in turn makes her smile. Overall, they would probably have a soft and sweet friendship, with Kai being able to temper Katya's endless energy just a smidge
jules: Probably the one to realize Dot and Katya are hopelessly flirting with each other. Katya loves hearing about all his conspiracy theories and getting into super hyped and friendly debates about them. They would spend a lot of time talking about music, and Katya loves hearing Jules sing. She would definitely want a duet.
remy: Katya would adore Remy because she can be responsible and Katya does not. Remy would probably find Katya's short attention span and lack of organizational skills a bit annoying, like she really is picking up after a child. They would have a relationship similar to a mother and daughter, though it would definitely be a pretty good friendship where they can balance each other out. Remy keeps Katya's head on straight
haneul: Katya and Haneul definitely sit next to each in art, and they definitely talk about nothing but that (and maybe music, from time to time). Katya loves Haneul (as she loves everyone else in her life) and likes talking to him. Katya makes it her mission to get Haneul to call her a friend (or something remotely affectionate) because she wants to be there to help him and he's just so closed off.
david: Katya thinks David is cuddling. Music lover? Check. Cuddles? Double check. He's laidback to Katya's boundless energy, and they would make a dynamic, fun-loving duo. Would totally badger him to play the violin instead of the guitar at one point, or do a duet with her on piano