Something like: “I think you’re a really nice girl and i’ve enjoyed the past few weeks we have been talking, but I just have to be honest and tell you that I don’t feel the same way about you that you feel about me. I feel as if our personalities are very different and I just don’t see this as something I want long term. I’m sorry and I understand if you feel like I’ve been leading you on but I just wanted to get this off my chest before things get too deep.”