Honey...if you don't tell her someone else eventually will because I can assure you someone else knows. If you tell this guy you love him then I can bet he has told his friends. Someone WILL tell her. You have to be the one to tell her otherwise you WILL lose your friend. It will be 100000 times worse coming from someone other than you. Do yourself and her a favor talk to her and tell her. Her getting a little angry but forgiving you is a lot better than hearing it from someone else and then confronting you with it and having a big ugly argument and no forgiveness later don't you think?