Ah yes, the old “Let’s really party” conundrum. You love your boyfriend and want to make him happy, but you’re not sure what adding this other lady into the mix will accomplish. It wouldn’t exactly be cheating on you as you would know everything that was going on (theoretically), but it wouldn’t exactly be staying faithful as, well… you get the point.

Regardless, once you change the sexual guidelines of a relationship, you have to change the relationship itself if it is to survive. Open relationships can and have worked long-term – but both parties play an active role in deciding those ground rules. This is not what I am picking up from your situation. I am hearing that your boyfriend has a longstanding fantasy (and don’t even get me started on the unending silliness of the threesome fantasy – pragmatically speaking, multiple partner sexual situations are often flummoxing as there are simply too many cooks in the kitchen. We were built to go one on one for the most part) and has finally gained the confidence to actively seek it out.

Furthermore, what is really to be gained if you were to oblige this request? You would be introducing a new sexual partner to your boyfriend – would you really be surprised to hear about them carrying on outside of your presence? Maybe you and her will really hit it off – who knows! The point is that once you take a monogamous relationship and turn it into something new, that relationship has, in its very essence, already ended. Which is not to say that a new one can’t replace the old one – but at the very least, that old one is gone.

There is no way that I can see that sort of request being an appropriate anniversary present. Anniversaries are about celebrating the union between you and your lover – not about satisfying one or the other (that would be closer to a birthday present). So at the very bottom of everything is this disturbing trend in your relationship – this is about him and only him during a time which is explicitly about you two, and precisely you two. Sexual exploration is wonderful… but isn’t this about exploitation at some level?