How do I stay close to my best friend?

My best friend and I are drifting apart, ever since we went to different universities. Before I had her I'd never been really really close to anyone - I could talk to her and confide in her about anything and everything and vice versa. Don't get me wrong, I have loads and loads of awesome friends who I love so I'm never lonely, but I'm just a bit saddened that she and I aren't as close as we once were and that I haven't formed a close friendship with anyone at uni. When we meet up we always have a good time, it's just never quite the same as it used to be. How do I stay close to her over a long distance? xx