My boyfriends ex...a little too friendly?

Okay, my boyfriend is like, the best guy in the world, nice, funny, smart and H-O-T!!! he has alot of girls with him all the time and asking him out but he is faithful and i trust him... but there is this one girl who is a slut...seriously... and at the beggining of the year we were friends and then she started to hang out with him, and yes they both liked eachother and it died down... now he is with me and we are happy, but she still likes to hang around, flirt, give him hugs, be really close to him and i DON'T like it... now i don't want to seem like a very jealous girl and nag him and ruin this, i am just worried that perhaps this flame didn't really die, and maybe she is trying to rekindle it??? any advice?? thanks