I'm in love with my best friend
Why are you so in love with her?
I think she is hot, and she really cares about me.
If you tell her how you feel she might not share the same feelings towards you. She might only want to be friends and nothing romantic.
I think she loves me too.
I think you should ask her about it. She may be open to having a relationship or not. You never will know unless you ask.