Crush

My best friend who has a crush on me confessed a while ago. I told her I don't feel the same way, but I can't seem to stop thinking about kissing her and other cute scenarios in my head. It took me so long to admit to myself that I had a crush on her. I keep flirting with her but I feel like actually telling her that I have feelings for her, but I don't know if it's the right timing. Can anyone tell me how I should confess? :(