Like everyone says, why worry about a chick who obviously has insecurity issues!! For now it is the car, but if you were to stay in the relationship sooner or later it would be some other insecurity....like she would think you were cheating on her for some reason or another.
As for lookin at the pic of the other girl cuz she looks like your ex...that is just your heart mending...I think it is perfectly fine and soon you will be able to overcome your sadness.
Maybe you should put out an add "Must Love Camaros"
There are plenty of women out there who are just obsessed with the Camaro as you are!!