she knows how amazing the person she has is and she doesn't want to lose him because he's so damn perfect.
Two: she knows that there is a very real chance that the person she is getting jealous over is better than her in many ways.
No matter what you do when you have a jealous girlfriend you can not be mad at her for being jealous because it is not her fault. She is feeling insecure and you are not helping. Girls do not get jealous over nothing; there is a reason. she loves you and she doesn't want to lose you.
