Welcome to FT infrequent....flyer, great to see your first post and hopefully the first of many

On your question, unfortunately that wouldn't be possible. You have to book the return with both passengers, and once your wife doesn't show for the outbound her return would be cancelled. You can't book a 241 with one person out and two people back.

There is a great guide to 241 vouchers you can find here which may help you get some value from them https://www.flyertalk.com/forum/brit...er-thread.html