I'm sorry you feel so bad, I can understand why you're upset. But, you do have a trainer, and from the sounds of it your new trainer (not the guy) is helping Josie, right? I think Josie can learn to curb her aggression, and you are a good dog owner if you are willing to spend the time to train Josie. Maybe she will never like other dogs, but maybe she can learn to tolerate them.
I really hope this can be worked out and you feel better soon. Good luck!