I understood they knew each other at least partially, depending on the background of each, they are underneath the university after all. In the case of your character it'd make sense if she joined in later than the rest or just now began to know them.
I see it this way, given Kana and Naoma's age, they definetely encountered each other before and have been under a similar chain of command for longer, Alice likely came next, and y/c
@illirica would be the most recent.
We never really discussed it, but its kind of the vibe I felt from Aunt's starter, they work together, so they are at least acquaintaces- But nations make new allies so your character doesn't need to have an established close relationship with any of the other characters.
Then again those are my thoughts, I throw this one over to
@AuntRainbows 'cuz I might be making stuff up she didn't envision haha.