It is who she is, bro.
And yes, it is jealousy. It's a crappy feeling that gets expressed in very unattractive ways.
I wouldn't dump her, I would befriend more women (plates), and take them out. She should have no problem with that considering what she's doing.
She'll argue with you about it, because women are natural manipulators, but don't let it bother you. Just smile.
Chances are she's either naive about guys or she's aware and enjoys male attention - just as you would enjoy interested female attention.
Like I said, that's who she is. One thing I did when I was a true AFC was assume my LTR/GF at the time was incapable of being attracted or interested in other guys. I would get jealous, mad, upset, when things didn't vibe right or when another guy came into the picture. Instead, now, I simply accept it for who she is and not let it bother me. You can't force her to do something she doesn't want to do. You may be able to talk to her about it, about your jealousy and the problem you have with another guy, but even if you have every right to feel the way you do - you'll come across as weak, insecure, jealous, etc. and she'll be able to tell her girlfriends that (or this guy "friend") and use it against you. It's better to just accept it for who she is and act accordingly.
Don't dump her though just work on your self-esteem/self-concept/confidence/ego and get what you can out of it.