Advice needed

I am getting really uncomfortable about my friend's intentions. She seems overly interested in my boyfriend. She is always asking about him and he had been away for a few days. She phoned me asking was he back and could she meet up with the both of us. I said no cos I wanted some alone time with him. I had seen her only the previous night also.
When I have invited her along, she seems to be overly flirtatious and I am getting fed up. I don't want her along at all when he is there and the way she is behaving is killing my friendship with her.
She once admitted that she thinks "all is fair in love and war" and would make a play for another woman's boyfriend or even husband. Her current boyfriend is someone who was previously with a former friend of hers, and she is now not happy with him.
So...I don't want her along at all when I am with him, and the way she keeps asking about him is making me decidedly uncomfortable. It's making me feel anxious and depressed. I like to see her otherwise, but quite often when she is with me on my own she makes phone calls to other people and seems distracted. I have asked a couple of my boyfriends friends what they think and to tell me if am just being paranoid, and they said I am not and to be very wary.