Talk to her. Communication between the two of you is key for mutual understanding. I remember when I broached this subject to my wife years ago. Being the more possessive one in our relationship, she had similar concerns as your wife does. In fact, she downright hated to see me talk to another woman, let alone having sexual relations with one.
Nevertheless, we continued talking, and I gave the explanation that regardless, she will always be my wife. We have lovers, but she is my wife and I am her husband. We have sex with lovers (oh, do we have fun with them), but 'making love' (meaning not just sex, but emotions - you guys know how corny that sounds right?) is just for the two of us. Lovers don't have rights and responsibilities to each other beyond the sex, but couples do. You have to drill this into her. But, moreover, you have to believe in this too. You have to hold fast to the rights and responsibilities as a husband. If you're into this just because you want to screw around, then don't. That's the same as an excuse to have an affair, and that's the seed that will break you up. Might as well just have an affair or just have a good time with a professional (without your wife knowing), mate.
When my wife and I finally made our decision, we made an agreement. Whatever happened, we will always be with one another. We never do anything without the other's knowledge and consent. The result? Our experience had further developed, from what was a mere soft swing with another couple, to her hotwifing, me being cuckolded, to experiencing everything.
The talk you are going to have will not be short, it will not take place within a short period of time. It will be a long talk spanning several days/weeks/months where the two of you need to understand each other, where you are, where you're coming from and where you are going to.
Understand this, you should know that swinging/cuckolding/hotwifing is a serious decision for the both of you. The both of you should make a rational decision about it. So talk. That's my suggestion.