"Sie ist nicht deine Frau?"
"Is she not your wife?" and "She is not your wife?" are two questions you would use in different contexts. For example, if a guy said to his friend, "If I go to Barcelona this summer, I would not take Karen with me." And the friend could say, "Is she not your wife?" (Why wouldn't you take your wife?). And in a different context, there are two guys at a neighborhood BBQ gathering. One guy says to the other, "You've met Lucy, right? I think you guys should date." "She is not your wife?" "No, silly. She's my sister."