My GF confessed and now I’m torn

I’m a straight 26yo guy, in a long term relationship with a loving GF.

My GF and I hung out, teasing each other about different fantasies we’ve confessed to each other over the years, when she suddenly brought up a few new fantasies for her, including fucking someone older and watching me being with a guy.
I was surprised and didn’t give it much thought, but now I have the visual of a strong older man turning me into his bottom boy implanted strongly in my head. Should I tell her? Should I act on it?