You don't, but if she is then that is her problem. It is your ex-girlfriend, you should have moved on.
If she tells you.
Justin Bieber's Ex Girlfriend's Full Name Is "Caitlin Beadles". =]
you already answer that to your self
If he has nothing to do with her and you have the trust in him when he says that he is.
To say: "Just to let you know, I dated this girl before you; but we are through now"
No, just tell her that your ex wasnt the right girlfriend that she wasnt right for you.
i am a girl so i know what im talking about if all else fails introduce her to your new girlfriend and snog this new girlfriend in front of your ex
they tell you :) I know that didn't help but i tried!
you know there over you if they flirt or date other guys
The only way to know if your ex-girlfriend will think about you when you leave school is to ask her. Your ex-girlfriend may or may not think about you when you leave school.
he is simply confused