Introducing characters - how quickly is too quickly?

So after having a friend look through a snippet of my rough draft, she told me that there were too many characters introduced within too short of a time period, and she couldn't keep them straight.

Well, my book might have 9 (yes, holy moses that's a lot) characters. And I'm rather invested in ... oh, all of them. So, now of course my problem becomes how to introduce them all without confusing the reader (that'd be you). 

Of course, that means RESEARCH! I am quite in love with research, and it might lead to a little bit of procrastination...

Anyway, what I found is this:

1. If you can, introduce them a few at a time, slow and steady wins the race. 

2. Give each character a prominent trait/descriptive (NOT NECESSARILY PHYSICAL, as one article mentioned here, cause 'been there, done that') so that they stick in the mind, and repeat it (along with their name) every time you see that character in the next few scenes. Describe, rinse, repeat... okay, maybe that's not how it goes. But you get the gist.

OR, and this one is kinda fun, but doesn't really work with my book:

3. Deliberately confuse the reader. My research referenced the beginning of 'The Hobbit' where Bilbo is confused with meeting 13 dwarves all at once. Granted, I've never read The Hobbit, couldn't get past the lengthy descriptions...but that's neither here nor there, because you get the idea. Right?

Now comes my dilemma -  I'm good with introducing my peeps a few at a time. They get their plot relevant backstory, introduced with 'action' (I think?), and a defining physical trait (oops, guess that's not entirely ideal). But they're all arriving at school around the same time. It's relatively easy to mark a certain point in time when switching POVs. For example - when Cassie arrives at Raven's room, she bangs on the door, girly squealing ensues. Then when you meet Ryder in the next chapter, he walks into the building and hears the banging and squeals in the distance. Easy peasy. But Felicity (Cassie's roommate) runs into Raven and Cassie before I introduce her and she gets her own intro scene.

So now my problem is - 

        A. Do I say "Cassie's roommate" and then later you see Felicity's scene and find out 'oh, that's who that was'? 

            OR

       B. Do I show that little snippet of "Hey Felicity, yadda yadda" and then later get the rest of Felicity's intro?

My research above said that I can "mention a character not present in the scene, before he is properly introduced. Then, when we meet the character, we already know something about them, so it's easier to remember this character as distinct from the others." So I kind of like my option A, which means REWRITING. An author's favorite thing to do. 😅