Most Helpful Guy
So, you don't want to flip a table and go crazy on him just because he met a girl and they have a lot in common. I have a lot in common with all of my friends so it's fine if he says that about her.
But he is your boyfriend so don't feel bad about communicating your feelings to him. Guys and girls both get jealous and sometimes it just feels really nice to talk about it and have someone listen. Your boyfriend can probably make you feel better than anyone on this site.
Most Helpful Girl
You can't stop him from falling for someone else.
You have to be confident in yourself and your relationship, otherwise it might push him in the other direction.
I think it is really weird that he would say that.
Either he just assumes you know that he means as a friend, or he blatantly doesn't care about how that makes you feel.
Maybe you could talk to him about it. Don't act whiny or needy, don't beat around the bush, just say "Hey, are you interested in her or think you will be?" something along those lines, and see what he says.