How do I break up with a girl who is madly in in love with me for no reason?

Me and this girl have been dating for about 2-3 months. I don't know how, but ever since the first day we started dating, shes always said she loevs me alot. I'm pretty sure she actually does to and is not just saying that. When shes drunk, she tells me how she would be severly depressed if I was to break up with her and she always talks about being with me for ever. I mean were only 15 and I really just don't like her anymore. I don't know how to end this at all. She has no idea this is coming and it's going to kill her. Any advice?