LOL, Darkness, this is funny.

Darkness, that girl? You need to sit yourself down and tell yourself "do not let that person bother you!" In fact, instead of being angry "make" yourself be pleasant you are certainly smart enough to practice doing that. You can "learn" you don't have to like a person to be nice to them. I also think that girl probably triggered you because your mother was negative like that. And now you are having a negative cycle, can you see that?

Make a note of this, I think you need to slowly identify these kind of triggers so you can work on taking the power out of them more and more. You know, it's ok that you vented here, this is you having a negative cycle, better to vent it "out" than turn it inward. This isn't so much about the people you encounter, it's the anger you experience that you need to work on gaining more control over. Also, you need to learn how to sit in a classroom even when you get triggered. You need to feel you CAN sit in your own space despite things around you that can trigger you. Hun, you are smart enough, you can do this, you can LEARN to do this. I told you about my brother remember? Well, he had to learn how to do this, he often could not afford to eat, did not always have a place to sleep and napped in the library. You know what? He did make it and he also got the mercedes.