It sounds like most of us (despite all the stories that swingers are everywhere!) have similar situations with our partners.
I think an important thing to consider is the term fantasy. It is still ok to fantasize about something and not do it or pursue it. If you make your partner comfortable in that clearly defined aspect, perhaps she won’t be as shut down.
For example, I am into exhibitionism and group, specifically MFM. Prior to our relationship, I had several intense and enjoyable experiences doing MFM. I was always brought in as the bull/stunt cock and never experienced the playing the partner role, but the overall dynamic still feels hot. My wife is not into it. We watch porn a couple times a month and every couple times of those sessions, I will say something like, “I want to watch some hard fucking or intense sex,” and I will pull up a hot mfm scene. Even when we are watching a normal couple scene, I will whisper something to the effect of she likes his cock or would love to be sucking his cock instead of her. I am not super jealous about that stuff, so it plays off. Additionally, there are times (less frequently) that I pull out a toy and double team her with the dildo, usually her sucking it while I fuck her. These are activities of just her and I that we share alone. Completely different than saying something like, “I heard Tom and Jane are swingers. She is so hot. We should have them over!” That can be far more intimidating and challenges to her role as your partner.
I write all this with the (internally justified) thought that my kink isn’t that weird. If you are into bukakke or fecal or more aggressive stuff, the dynamics might be too far apart