06/22/2012 04:00 pm ET Updated Aug 22, 2012

Kate Middleton and Prince Harry: When Is It Just Flirting?

Duchess Kate Middleton and her brother-in-law Prince Harry were recently caught by photographers exchanging "flirty" glances. The pictures were taken during the Diamond Jubilee celebrations in honor of Queen Elizabeth II. Standing with the royal family on that famous balcony, Kate and Harry swapped what appeared to be secretive smiles and a knowing laugh while William had his head turned. Only the media would peg this as possibly inappropriate flirting instead of the more likely scenario that Kate and Harry were just having a good time, as a brother-in-law and a sister-in-law often do. But it does raise a question that many people ask: What constitutes flirting? And to take that a step further, when does flirting cross the line?

The answer is that it depends. Flirting generally gets a bad rap, especially if you aren't single, just as Kate's smiling at someone other than her husband drew negative attention. But the truth is, whether you are unattached or committed to someone, putting yourself out there with other people of the opposite sex and making smart conversation helps you feel desirable and confident. It creates positive energy that can make you feel good about yourself.

If you are already in a relationship, however, you have to make sure that you are both comfortable if either of you flirt with other people. One of my male patients, for example, became upset when his girlfriend would reach out and touch other men while joking with them in bars or at parties. When he asked her about it, she assured him that she is just a "touchy feely" person and it meant nothing to her. But her boyfriend didn't agree. From a guy's point of view, he felt that the touching took the flirting to a different level. In their case, they had to set boundaries, which can be different for each couple, to make sure that whatever went on didn't make them feel bad or doubt the other person's feelings. Flirting definitely crosses the line when it becomes a sexual invitation to someone you are not in a relationship with.

If you are able to stay on the appropriate side of the line, though, then you can make sure all that heightened sexual energy is stored up for your partner whom you will share it with later. If your relationship is solid and you feel you are being given enough one-on-one time, then that generally works. Sometimes watching your partner flirt can give you a sense of pride. It can even be a turn on.

But if it makes you feel threatened, then it's a good idea to talk about how you are feeling in order to handle it. If the foundation of a relationship isn't strong, it can increase your feelings of doubt and mistrust. The person doing the flirting might feel good, but it can make the other partner feel insecure. If it seems that your partner is flirting with everyone but you, or you are flirting with everyone but them, then you might want to look at why that's happening and think about what's going on between the two of you.

If that is the case, it is a good time to take stock and realize that rather than looking outward, focus your energy inward to work on strengthening your trust. You can do this by being affectionate, complimentary and expressing your love toward each other. If you still feel uncomfortable with your partner's flirting with others, it can also help to set ground rules, as my patient was able to do with the no-touching rule. For someone else, a little conversation might be okay, but if it goes beyond that and someone offers or asks for a phone number, the answer is no. Everyone has a different level of what they can tolerate in terms of their partner's socializing outside of their relationship. You don't want it to be divisive or take away from you as a unit. The goal is to be clear about what your partner's behaviors mean to them, and to make flirting work as a positive rather than a negative for your relationship. And there are times, of course, when people might just be being nice to each other. If William thinks Harry is making a move on Kate, then that would be a huge problem. As long as he trusts his brother and knows his marriage is solid and secure, Kate and Harry can smile and laugh all they want.

Please tune in to "Let's Talk Sex" which streams live on every last Tuesday of the month at 2 PM EST, 11 AM Pacific. We look forward to listener call-in questions, dealing with relationships, intimacy, family, and friendships, at 1.800.555.5453.

Connect with Dr. Jane Greer on Facebook, at, and be sure to follow @DrJaneGreer on Twitter for her latest insights on love, relationships, sex, and intimacy.