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.
She asks your friends how you are doing, if you are seeing anyone and if you ask about her.
don't do it.
If you wanna know then just ask her. She might be honest or if shes lying then u would know.
Tell her that you still have feelings for her and you know she does too. silently walk away. if she actually loves u she WILL come back. and that last answer was so mean.
if they have a lonely look on there face but when hes near she tries too look good
he is simply confused
say how much you love her
there is nothing you can do
If she keeps eye contact or if she lets you know... maybe if her best friend tells you, you'd know the truth... but for now, just ask her or tell her
Because he still loves her and because he never really has forgotten about her.
if you notice he/she gets weird when you talk about your boyfriend/girlfriend then you know they still love you but if they dont get weird when you talk about them then they are fine with you going out with someone else because they have moved on.