Mallory Little (this journal) is a 5th year Hufflepuff and muggleborn. She's very bubbly and sweet. I don't think she'd really know Caleb, though. Probably a 3 at the most.
Trinity Macmillan is a 6th year Hufflepuff. She can be a little moody towards boys. Her ex was a hugeeeee jerk to her. She probably wouldn't be a big fan of Caleb's. Either a 3 or 4.
Kerrigan Flint is a 6th year Slytherin. She's kind of like the Blair Waldorf or Regina George of Hogwarts. She's not really all that popular with people outside of Slytherin though. I'm sure she'd get along fine with Caleb, maybe even flirt with him. 2, 5, or 6 could work.
Sinead Finnigan is a 6th year Gryffindor. She comes off as a dumb slag, but she's really not either. She just likes to flirt with boys and have fun. She probably wouldn't have any problem with Caleb. But he'll probably think she's annoying. Probably 3.
January Moonbeam is a 7th year Ravenclaw and muggleborn. She's pretty nice to whoever is nice to her. But since her latest crazy breakup, she's a bit on edge. She's probably a 3.
Molly Weasley is my last char. She's a Gryffindor graduate and tends to get on her family's nerves. She's a bit motherly and scolds people for doing bad things. Probably has no idea who Caleb is lol.