Why would my ex and my 'best' friend get together?

dont let it stop you. You must be aggressive and follow her around and make her do what you want. Be a man and lead the relationship ths is your girl and you need to relive ual tension by sleeping with her. So go in Peace and tell her she has to be with you or else things will get sticky then send her 15 dozen roses or flowers and make 12 thousand papers saying you love her and p it all over the city.