I commend you, Mayson, for caring about hurting the girl. That said, it's time to set your boundary by telling her straight-on and with no hesitation that you are not interested in a relationship. As in, "The way you're acting toward me is really bothering me. I don't want to hurt you, but I'm going to be very honest: I am not interested in a relationship with you. Now please leave me alone." And walk away. It will sting her, but believe me, she'll survive and you'll be able to enjoy going out again.

Let us know how it goes.