Unlike in cases were folks book for others with no or lower status, you both seem to have equal status so I can't see the hotel having much of an issue with extending the benefits.

Personally, I would drop the hotel a note that your wife booked, but you (the second guest on the reservation) will be staying and that you have the same status than your wife (supply your IHg number for their info). That way you will be on the safe side.