I will draw many frowns but firstly if she is aware that this causes issues in your relationship then there appears to be a lack of caring on her part. As for her ex he obviously does not care either about your relationship which means there may be no boundaries. Do you have a right to be concerned, yes. In every case where I have know men and women "friends" over 80% have ended up in failed marriages or affairs. It never seems to fail that eventually one or both end up wanting a little bit more. Are there men/women friendships that work, yes, but not many as it is the nature of the beast.

If you have had the jealousy discussion and she prefers to ignore it then you need to move on as your issue will just continue to snowball no matter how much counselling you get.