The best course of action: just relax and let her do what comes naturally. If that means your wife putting her legs up in the air and letting her black lover inseminate her like a brood mare, that is only nature taking its course as God intended. You should of course be present while she is being serviced by her black bed partner. You should calmly and lovingly encourage her as her sexual passion increases, and arrange that an unobtrusive video camera is running so as to preserve those precious moments when her passion swells into orgasm and the bull ejaculates his semen into her womb.
God willing, a few weeks later her belly will visibly ripen with the seed of her interracial passion. And when she is in late-term pregnancy and her round, swollen, gorgeous belly drops, you will be so excited that you will do everything you can think of to proudly show her off in her highly pregnant condition. You will insist that she take walks in town with her black lover, both of them hand-in-hand, with the Negro lovingly caressing her belly as they amble about in public places where you know your friends are likely to see them. Take photos of those occasions and post them on the Internet so that other interracial fans can enjoy them. And after the blessed day your sweetie delivers her baby (or twins, if her black man is as sexually potent as he should be), you can proudly show the baby (or babies) off by parading a stroller down the main street.
At that point, you will understand. The only remaining course of action will be to allow her to breed with a black lover again. And again!