Cassie I can kind of see as being kind to everyone but Rachel being her only close friend, and not getting invited to group things unless she was invited as part of a set with Rachel--but Rachel probably knew everyone in school. I highly doubt that Jake would've had that "leader" reputation if he hadn't been a fairly popular guy, also. Marco, obviously, as class clown, would've had a lot of friends but it's also possible that Jake was the only one that was really close to. (I have a friend who was the class clown in high school and that was how she described it, anyway.)

And while I can see them all kind of cooling off a lot of casual friendships in the interest of keeping each other and said casual friends safe, it struck me as weird that they wouldn't, to an extent, keep up a pretense with their closer friends. Like, they avoided hanging out as a group at school but Rachel cuts ties with Melissa, who was a fairly close friend? Where is the logic there?

(I recently watched the TV series and while it DID have lots of flaws, and I need to make a post about it, they actually did bring Melissa back later in the series and it worked very well.)