I've never had this happen to me, but tell her if you can have a private talk. Don't keep it a secret for long or things will be VERY awkward between you two. and she will have probably suspected it already by how you have acted or talked to her recently, unless you're really good at keeping secrets. Tell her why you love her and that you've developed feelings for her, and wanted to let her know to see if she liked you back. if she does, go out with her but if you break up later on, try to keep your friendship. if she says no, but still wants to be friends, stay her friend. She might change her mind, and anyway, there are tons of other girls. It will hurt but don't let it ruin a great friendship. also, if she rejects you, don't keep on asking her. if she doesn't like you, you can't make her. only herself and time will do that. good luck!
I think i am in love with my best friend but am afraid to tell her, any advice on how to approach this?
