Relationship advice, please?

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I'm an 18 year old who is moving away to university this autumn. I've had a girlfriend (ree get out) for the past two months, and I've realised very recently that I don't like her enough to try and do the long distance thing. I feel guilty about this but I know that I can't help how I feel, just how I act. I'm inexperienced romantically and am a little immature in terms of romantic emotions, so I wanted to ask for advice about how to go about ending it properly.
Some context that might be useful:
It's her birthday two weeks from now so I feel like I need to do this now, because I can't dump her right on her birthday and I'd feel insincere staying with her longer than two weeks. We agreed to have another chat about what to do closer to me moving away, but I already said I wanted to stay together over the phone when I was REALLY drunk, and upset about a drunken argument with a close friend. She didn't express an opinion at that time, however. I've just gotten back from a trip away where we couldn't have much contact due to phone contracts and wi-fi availability. I haven't seen her since I set off on this trip, around two weeks ago.
Basically, is it appropriate, considering above context, to ring her up in the next couple days when we're both free, say I want to have "that chat," drive her somewhere that same day and admit how I feel?
Writing this out, I feel stupid and certain that the answer is, "yes," but I really don't want to hurt this girl more than I have to.