Act confident. If the girl's motive for flirting with your boyfriend in front of you is to make you feel insecure, behaving that way gives her the satisfaction she's looking for. Don't give the flirt any more or less attention than she would otherwise receive from you. Likewise, don't cling to your boyfriend or show other physical signs of insecurity.

Look at the flirting in a different way. Sean M. Horan, a faculty member in the College of Communication at DePaul University, noted in an article for Psychology Today that flirting isn't always about starting a relationship or about sex. It's possible that flirting may simply be the girl's way of building her self-esteem or getting something she wants from your boyfriend -- like his notes for the upcoming chemistry exam or his best friend's phone number. It's probably not personal, and even if she would like to steal him out from under your nose, she can't -- not without his permission. Of course, any worthy boyfriend isn't going to call it quits because of a random flirtation.

Appreciate the qualities in your boyfriend that make him flirt-worthy. Being thankful for his general gorgeousness and winning personality will bring you more peace than feeling angry about another woman's possible overtures will. After all, you could have a boyfriend no other woman would ever look twice at, and that would be an entirely different problem.

Keep your anger in check. If you feel your muscles becoming tense, your heart beginning to race or other early warning signs that you might be about to lose your temper, remember that she who keeps the calmer head wins. Tell yourself you'll talk to a friend about your feelings as soon as you have the opportunity.

Talk to your boyfriend about how the other girl's flirting makes you feel, especially if it's a recurring event. Resist the urge to go on the offensive and accuse him of encouraging her. Simply let him know that her actions make you feel disrespected and allow him to decide how to react the next time the situation occurs.