What is the point of talking about your friends behind their back? Honestly, I've never understood it. If you have a problem with one of your friends just tell them to their face. Don't go through other people to try and avoid conflict. You are both adults and in college, just talk about it!
Two human beings can have a regular conversation without getting aggressive in anyway. Maybe if you brought your problems to their attention, they could try and fix whatever it is you are mad at them for. Leave your High School drama at home and put on your big girl pants and confront your issues. Who knows they may even respect you more for saying something. Going behind someones back is the weakest thing a person can do. It's highly annoying and juvenile and you should have probably grown out of it years ago.
I'm not saying this to be mean or harsh or whatever you want to call it. I'm saying it because there are people in their 20s who are still doing the same things they did five years ago.