How quick can love at first sight happen?

I know for certain that love at first sight exists because it has happened to me. It has only happened once, but it did actually happen. I saw this young woman across a crowded room and fell in love in an instant. Everything about here communicated what I valued most in a woman -- gentleness, tenderness and lightness of spirit !! And, this was communicated in her body-language, her deportment, her hairstyle, the way she dressed and the way she moved. Wow !!