How do I tell My best friend that I'am in love with her?

So me and her have been best friends for 3 years now, over the years we've helped each other out with realationships, and we tell each other everything and all our feelings, and when we feel sad or upset we always hang out and talk about it. We have everything in common, Were basically are alike, and she calls me her big brother. and For the past 3 years I have never had any feelings for her more than freinds, I always seen her as my best friend. Then one night I stayed at her house and we ended up doing stuff together and we were completely sober. The next morning it wasnt as akward we just laughed about it, then later on that day she told me she will never be able to look at me the same? and i told her i dont kno what i was thinking and i felt weird about it, then she said she only went with it cuz she didnt know what to say or do that night while we were doing stuff. And after that night I have mixed feelings and we hung out alot more and now I just realized i fell in love with my best friend, and I am scared to tell her, cuz If she doesnt like me then we will pry no longer be best friends after that cuz she will know i like her and it would be akward... So i need some help here, I want to tell her but im scared and i dont wanna end up watching her goin for some other guy like in the movies...