My girlfriend is a very jealous woman. She doesn't want me thinking any other girls are good looking at all. She is pretty insecure. Kinda chubby, but she thinks she's fat. I keep on telling her she's not fat, and I love her figure. Not too long ago, we were with some friends, and one of them aasked her if I could answer a question, and she said yes, the question was if I were single then would I fuck the other girls there. And without hesitation I said yes, however she thought I was going to say no, and she threatened to break up with me. She also gets jealous and angry of this one girl I had a fling with for a little while. She once asked me what I would rate this other girl, and I said a 6 or a 7. Then I heard her gasp like she was hurt by what I said, and I panicked and said " but you're a nine baby!" and this started a very heated argument. I believe this shit is super unhealthy. It all stems from her insecuritys, and past relationships. Like I seriously believe that I'm going to marry this girl, the good outweighs the bad, but is there any way I can get her to stop being this damn jealous?

Tl;dr: girlfriend is a jealous type, how do I stop this shit?