How do we become good friends again?

[Andrew]

I have a friend (that is a girl) that I made in one of my classes in first year at university. We are now in third year, but we seem to have drifted apart.
I'm not entirely sure what happened... maybe it was because we started taking different classes, had slightly different social circles, etc.
We used to hang out sometimes, help each other with homework and stuff like that, but now I'd be lucky if I had a 1 minute face-to-face conversation with her.
I don't like her more than a friend or anything, because I already have a girlfriend. And now you're thinking, there's the problem - but I've had this girlfriend for the entirety of the friendship.
She recently got a boyfriend over the summer, and this is where I think the issue is coming from.
Perhaps this guy isn't a big fan of his girlfriend having guy friends - but I just don't know how to confront her about this issue. I don't want to sound like I'm needy or that I'm secretly in love with her or anything.
I just miss her and wish she was back in my life - again, I don't want her to be my girlfriend (I've already got a perfect girl) - I just want my friend back.