You should express to her that this isn't what you want, you aren't like her ex and you believe this can still work. Then say that even though you don't agree, you understand that this is what she wants, and if she's sure then you won't pressure her. I'd finish off by saying that nothing has changed for you, and if she changes her mind to give you a call.
Basically make sure that she understands that you don't want to be apart from her, you're not like anyone else, and that you will give her some time to work out what she wants. Then put the ball in her court to contact you if she's still interested.
Then all you can do is stop trying to contact her and hope that you've made enough of an impression on her that she will realize how valuable you are. If you haven't, then there's nothing you can do to change her mind. You won't be able to talk her out of this, and if you try, you'll justify her fears about men being too possessive. It's important that you don't hang around her, because if you do she won't miss you and have any reason to question her decision. If she doesn't call you within two weeks, then move on with your life and maybe you guys will meet when you're both truly ready.