the wife who vows never to sleep with another Jew, ever ever again.
the husband can simply cancel the bit of the vow that applies to him.
but not the bit that affects any future relationship she may have after their (inevitable) divorce.
If your wife is not just saying, but making a vow, never to benefit from any Jew, then the husband really ought to take it personally and not just cancel out her vow as it applies to him and carry on sleeping with her. The discussion about this also states that he doesn't cancel the vow with respect to any relationships she has after divorce. So even after she has left the relationship that caused her to swear off sex with Jews, she is not completely free.