Keziah: Probably knows Maura the best at this point. They're in the same year, so they share Arithmancy, Charms, History of Magic, and Transfiguration. They're also in the same Social Circle so there's no ignoring one another. Keziah's probably nicer to her than she'd otherwise be because of her family.
Cameron: This will be his first year as a Beater for Ravenclaw's Quidditch team, so they'll have plenty to do together.
Nora: Is also a member of Cooking with Charms. She takes her baking pretty seriously (her journal name isn't bakesaleofdoom for nothing) but I don't think they need to be mortal enemies or anything.
Lottie: On the surface, has nothing in common. No classes, no clubs, no House, no Social Circle, no common hang-outs... But she's cheerful and likes cheerful people, so even if they don't know each other yet they can get to know each other over the journals.