What I want to say to my best friend at my wedding: "Dear best friend, He may be the 'love of my life', but you will always be my soulmate." --- but I would tell you "he may be the love of your life but you're my soulmate"
You've been my best friend for almost 5 years now and I love you more and more each day. Thank you for always being there for me. You have been my rock, my love. It's always you and me. :) Kisses, my sweet bestie