I'm a college girl and I feel left out?

I met really great people in my first year at my university and I simply love it. I became good friends with three girls and we sort of became a group. In the group I became really close friends with one of the girls. I just felt like I could tell this girl anything and that she would understand me. The other two girls in the group became close friends too and that was how no one really felt left out. However, at the end of the first year of college my close friend and my other friend sort of became more close friends (which is fine to me). By doing this though, they started to exclude me in conversations and other things. I don't know...Is it so wrong to just feel terribly sad about feeling left out? And about feeling like I've lost the relationship I had with my close friend?