does your wife need the elite qualifying nights toward her status? If not, I would make a reservation under your account and call in to Marriott Rewards team (not reservation) to have her points transfer to yours to complete the reservation (or you can go thru the SPG route and transfer online)

Reason for my suggestion is that before you show up, all the hotel will see is your wife Silver status. You can contact the hotel in advance about your Gold status, but that will only be just a comment added to your booking. When someone just run a "quick" report to process the upgrade and stuff, your reservation will most likely not on the list.

Hope this help.