Good you're talking about it. You may still be far away from "probably be totally up for it," even in magic Brazil. Maybe you can work on getting her with just one black guy first? Get her reading hotwife ir fiction. Maybe she can start writing these anonymous interracial fantasies down as fiction and share them somewhere. It would be a shame for an amazing body wedded to an openminded guy to go to waste on monogamy if you both feel monogamy for her is a waste--or at least a ground rule worth bending or breaking once or twice. Maybe in Brazil after all!
Where does it all come from? Maybe the desire to see hot bodies sweating and pumping in lawless fruition the way pagan Nature intends? Attraction meeting no bounds or boundaries from morality, history, or racial distinctions. Or these social constructs making it even hotter when Nature takes control and the hot bodies are in thrall to their wildest instincts. Maybe a seriously beautiful wife deserves to experience all that uninhibiting rutting in order to be her fullest self, instead of living inside the tidy distinctions of bland matrimony. Especially if her own husband hears the distant drums of black thunder and wishes to whisk his wife off to the mating altar and abandon her there, for the thick hard cocks of the black warriors to unleash her inner white slut and leave her a pleasured, plundered, possibly pregnant bundle of blacked bridal bliss.
But that's for you and her to work out between yourselves. I wish you two luck on your adventures. Me, I'm just taking decaf.