This isn't facetious - You were talking casually with that girl and it went really well at the time. Now you are saying you can't talk casually with female coursemates. Buy you already have done. So, evidently, you can talk casually with female coursemates.

Still need more info on the situation with the girl to understand it.

How long between hooking up and her texting you - let's leave it?
Was there other communication in that time? If so what, if not why?
What genders are these ’most' people?
Why do they think it is awkward to hook up with a coursemate?

Bonus questions: Is there really a social circle of girls? And why want to be in one?


Peace,

kowalski