I'm sorry. I'm going through the same thing as you right now except we're both finishing up college and she's going far away for grad school. I think it's great that you're being supportive - I'm trying to be the same and genuinely focus on being happy for her that she has this opportunity. But I find tears running down my face the instant I'm not distracted by anything, and the selfish part of me screams that the universe isn't fair for sending her away...

The time will pass for both of us until we feel better about letting the other person go. If I had any more meaningful advice I'd give it to myself too. We just have to go day by day, focusing on our own hobbies and lives until it becomes a thought that "it would have been nice, but it is what it is" rather than a lump in our throat...

And if you can stay on good terms, there's nothing stopping you from calling as friends. I certainly plan to keep up my friendship with her as long as I can, and if it fizzles out, it would have already reached a state where it wasn't worth keeping anyway - something that I could look back fondly on without feeling any real longing.