Take comfort in the fact that you've done the best you can to raise her to be prepared for college. It's an exciting new world for her, to learn so much about the world around her.
Yes, you are going to miss her, but she WILL be back. How far away is the college? Can she come home for holidays, etc to make the distance seem less?
Our youngest decided to go to college at a university that's close enough to home to drive (5 miles away). I have mixed feelings about that, because I'm thrilled she's home each night, I feel like maybe she would have done better to go out into the world and fend for herself, to be more independent. My other two have already left home, but are in the area, so we see them often.
The relationship changes when they leave home, but I find that it's for the better. You move from the relationship of a teenager and parent to two adult people getting along in the world. And then - you see the results of the years of nurturing in the young men and women that they become. It's pretty awesome really, though it still feels scary and sad when they first leave home. (plus, suddenly, you aren't as stupid to them as you were when they were 14, because they realize that there's a lot more to life than home
)