I haven't read all the replies, but here are some things I thought of.
Girls define and keep the social order in schools, mostly by being mean and nasty. Girl bullying is nasty because it is so insidious, and works by undermining the person with others and herself. It can be hard for teachers to see, and to pin down.
The girls who define the social order in highschool tend to peak in highschool. They will never be more than they are at 16, 17 or 18. At some level they know this, so they try to make everyone else appear to be less than they are. Smart people want more than highschool status, and go on to do wonderful things. I seriously doubt that Condoleeza Rice, Sonia Sotomayer, Elinor Ostrom or Carly Fiorina were the high status, mean girls in highschool. So, yes they are mean, but in the greater world, they are a trivial annoyance that will pass.
Congrats for being willing to stand up to them.