Losing a sure win (10 points to the best answer)?

I met this girl. We became quite good friends. I told her that I felt more than friendship for her and she rejected me. She told me to pretend like I had never told her so our friendship could proceed. I did and sure enough it seemed to go back to normal. Then I realized that it had not gone back to normal at all. In fact she was distancing herself from me. I was doing everything in my power to try and stay friends, without coming across as needy. I know where I went wrong (telling her how I felt ofc.), but why is she distancing herself from me. Is she afraid she might lead me on? The time we do spend together seems like before, but I can feel her drifting from me