Is it normal i love my friend and i cant be without her

i am 19 and she is 20 she is my classmate. we both were friends for more than two years for 1 and half years i said her like i am like her brother(big mistake) but she wont be often calling me 'brother'. we were like friends. i felt like a friend and everything was normal. she has a very good charachter. after 1 and a half year i felt that am n a deep crush with her few days passing and it became more. i cant control myself and messaged her that i had a thought of being a partner with you life long. she was upset and i suddenly gave up and said sorry it was just a thought flashed you are my friend like my sister dont mistake me(another big mistake). may be her reaction made me to say like that and hence it was a crush at that time it dissapeared after seeing her reaction. and even i said her not to speak with me coz she may be angry. but she didnt get angry and she said than "you are a good friend for me. i wont mistake you at all. you are a good friend". i too thought that she is oly a friend for me. but after 6 months i cant control myself in loving her day by day my love and care for her increases and she appears more n more beatifull to my eyes day by day. i want to spend my life with her forever. but how can i say this to her. in case marriage happens in my life she must be next to me. i dont want her to force and marry her it would be nice if she also loves me. but i cant miss her. am i wrong? how can i say this? wat would be her reaction and wat can i do next?