Over-protective Ex

I am a divorced father. I met my girlfriend months after my separation. My X is insistant about our six year old twins not having any contact with my girlfriend and her seven year old daughter... To the point of ugliness and threats of making my life a "living hell". She had a bad relationship shortly after our separation. Got her boytoy and his and our kids together after only about two weeks, broke up a few months later. I however, have waited over seven months to get the kids and my girlfriend all together. We wanted to be sure of ourselves and our commitment to each other before involving our children. They were aware of each other for some time as all the kids go to the same school and have met in the halls and such. But we just recently actually got together for a day of fun. Now my X is telling my kids that they will never see my girlfriend again and claims to want to protect them from any "emotional harm". Yet now all the children are hurt because they don't understand why they can't see their new friend(s). My girlfriend is hurt and my x is screaming at me through the phoneline. She can't see or is otherwise unconcerned with the emotional harm she, herself, is causing the people I love dearly. What is my best course? She is clearly fearful, jealous and controlling. I need some help.

Your X is probably jealous and does not want to feel left outside. She would be unhappy if your children had a happier time with you and your new girlfriend than with her. She is using the only power she has, the children.

She will only stop destroying your life if she is satisfied and happy.