Am I crazy or what?

Every time I go to my local supermarket this woman (around same age as me )  always smiles at my boyfriend and makes any excuse to keep going down the same isle as us! And again it happened just now hence why I am writing this but she only smiles at him I've smiled back before thinking she is being polite but of course it wasn't for me I just get dirty looks! I know this sounds like I'm a crazy jealous girlfriend but it's every time we go there and it's causing problems with my relationship and getting me down questioning my boyfriend why are u smiling back and he says he doesn't