Fell for my Bestfriend

My first day in my new school. I have seen her during my school days. When I saw her I got some familiar feelings with her. Though it is usual to have some feelings when seeing any already seen faces but this wasn't like that. I felt something in my heart that I wanted to talk with her and be with her always in my life. At that time, I do not know much about love stuffs at that age of 12. What all I wanted was to see her all day and to get along with her. Days went by and we became lightly bonded friends. Later when we gone apart after our schooling, I couldn't see her as she gone far distance. At those times, I really wanted to see her badly. I didn't have any info about her. I was really at a mad state. Later during my college days, I got to know about her. We got again in touch with fb and later phone calls. She became very close to me and eventually we became best friends. And its been four years of our friendship. Though its been a friendly relationship going on, there is something which have been nudging in my heart since the day I saw her. Whenever I see any girl of her age, that reminds me of her. Now I have self realized that I am in complete love with her. I couldn't propose her because she have no interest in love. She says that she will go with her parent's decision and she believes that "Love after marriage is real love". I fear that proposing may deteriorate the friendship. At the other side, I couldn't think a life without her as my life partner. I am really in a critical state. Guide me guys with this bestfriend-love.