If you don't like being jealous you can fight it this way. Put on your mind every single reason YOU should dump this bitch and think of what a great favor the other guy is doing to you and try to OFFLOAD her.
Don't let her play the "jealousy game" on you. When your gal starts her game, break off all contact, pick up another gal, and when the first one contacts you to ask what happened, you can tell her. Calmly, plainly, and without being threatening.