Best friends boyfriend help?

ok so my best fried bf has hung out wih me a lot sense he and kortney(my best friend) has been going out. and yeah i do like him but rite now hes going out with her. well he flirts with me and is always hugging and kissing me on the neck and once on the mouth. and i tell kort but she blows it off. i dont want her to be mad at me if he break up with her to go out with me. please help me