My gut sense is do not tell her about your feelings. You risk losing a friend.
Sometimes putting a toe in to test the water is a good idea.
Have you ever given someone a foot massage? Or a back massage. Some massage oil or something not too fragrant.
This can be something that you share and still not cross the line into sexually explicit actions.
If you were to talk with her you could talk about the idea of sharing a foot massage and see if she jumps at the idea or turns cold as ice. A foot massage is a toe in the water.
I think I wouldn't risk the close sharing relationship by confronting sexuality head on. That is a kind of relationship with closeness and caring and compassion that many would envy. How lucky you are to share that.