You wife won't earn mileage, and you'll be out the cost of the ticket if you do what you describe.

Call and have her ticket canceled. You won't get a refund, but you will get a credit for the cost of her ticket unless it is an "E" fare. You'll have to pay a "change fee" but it is better than losing everything.

Welcome to FlyerTalk, Britsok1. In the future, a more descriptive title to your post would help to generate more interest and probably more helpful responses.