this is a difficult one!!
You have to ask yourself if ingornace is kind, do you not want to know that she effectivly firts with someone else!! If this is all it is then don't get jealious, do you flirt with other girls and don't tell her, turn it around and look at what you do!!
In todays world if she is fit for other guys not to make a pass at her, its how she handles it!!!
Try to keep perspective, if she hasn't cheated on you and you trust her then ignore this or talk to her just pointing out that she shouldn't do it when you are there as its disrespectful to your relationship with her!!