finally worked up my courage to ask

So I finally decided that I have been hiding how I feel to my bf. There's this girl who talks to him and he flirts back. This started after we were dating he became friends with her. I have no problem that he is friends with girls and love all of his but the girl just gives me a bad vibe. I talked to my bf before about liking her sexual pictures that I see on fb cause he likes or commenting. He saw no big deal with this but if I did this to a shirtless guy pic on fb I'm sure he would be mad. So I'm just going to be straightforward and say "be honest with me I won't get mad but what's your deal with this girl? Do you like her, do you want to date her or do you just find her attractive." Does this seem good? Like I said I love all his other girl friends and never would block him from talking to someone. It's just been bothering me.