It is very hard to keep a threesome going. I learned that when I was 5-7 and had two best friends; we were always splitting and two people going off together and leaving the other person. But through it all two of us lived closer to one another than the third person lived near us and so that meant the third girl was left out more often just from logistics. It sounds similar to what is happening with the other two girls having classes together, they are having experiences you cannot be part of?

I would look for friends in your classes and dorm (especially dorm for going to the dining hall to eat?) and maybe just come up with a ritual event to get together at; sporting events or parties, etc. Maybe you can form a study group that meets at the library a couple nights a week? Being in different dorms in different classes too is not working in your favor for constant togetherness. I know my best friend in high school was just one dorm away in college but I mostly saw her when we were home on break or when she needed to borrow a shower because her dorm bathroom had crabs We are still friends today, 45+ years later but she lives in Arizona and I, in Maryland (the state we were in high school and college together). I predict the next time I see her in person will be in 2018 at our 50th high school reunion.