You can't "know" for sure without mind reading. You can watch for signs or ask her though.
you know there over you if they flirt or date other guys
If he has nothing to do with her and you have the trust in him when he says that he is.
he says he thinks the world of her
you know what im sayin
You don't, but if she is then that is her problem. It is your ex-girlfriend, you should have moved on.
ask them
If he has moved on and has a new girlfriend it is time for you to realize it is over and move on as well.
Maybe your girlfriend isn't over her ex husband.
you never know..... men are a mystery
there is not much you can do you just have to get over them both
If she tells you.
she is your ex-girlfriend so,let her date leave her