Does this girl not want to be my friend, or am I reading in between the lines too much?

I'm in university, this girl who I thought was my friend or who I hung out with for a while just kind of switched up on me.
Like she leaves me out of conversations, she hangs out with the other girls (we live on campus and have all been here 7 weeks) but doesn't come over to my room, when I try talk/initiate conversation it's mostly a straightforward sentence, one word answers or nods.
But with the other 2 girls she's talking, laughing, telling them her stories.
I haven't done anything to offend this girl, maybe it's cause I'm not popular. What to do?