It’s nice you are thinking about her feelings. I surely remember my first time with another girl, it was a threesome and it just happened. I didn’t over think it, it came naturally as a threesome could be. My friend and I shared a guy and what happened was just a progression of the act.
My more recent swinging was to please my husband, he never saw two women together. I’m not sure if it was the right reason even if it did lead us to many fun times. That new first time wasn’t what we planned, not the Unicorn we searched for, we ended up with a couple, she was sweet, he wasn’t. My husband got to watch and as a bonus to him he had sex with a younger attractive woman.
We have since been with others looking for what we looked for. I can tell the ones who are doing it for the husband, like I did. Over the years I’ve learned to ask the woman questions to make sure she isn’t being forced to do it. Many are doing it just for him, I hate that. Sounds hypocritical because that is why I did.
You are having fun with friends you have already been naked with. You have seen the friend naked and had sex with her. You have watched your wife have sex with someone. The hardest part of swinging is behind you, that first time. You know she is nervous, she has asked you to not watch. My suggestion is for you and your friend go out for a drink and leave the ladies home alone. Let your wife be comfortable without the extra pressure of you watching. These friends will be there for more fun. If your wife can get by her first time with a woman and she enjoys it you will get to watch during future visits. I’m thinking you may get to watch right after you get back to their house with your friend. Let her enjoy her first and you will be rewarded.