A similar question was asked earlier today: Bonvoy boundless + platinum status?

Nobody responded to either question because there's not a firm answer.

FNCs must be used by the person who earned them. The reservation will be in your wife's name and will be associated with her Marriott Bonvoy account. So, technically, only Gold Elite benefits will apply.

However, she can add you to the reservation as the second guest. She can ask the property to note that you are Platinum Elite, either before arrival and at arrival (or both). She can request nicely that she hopes that, under these circumstance, the hotel will provide Platinum Elite benefits, such as breakfast and/or lounge access, depending on the brand, and possibly will consider the Platinum Elite guest when assigning the room (possibly with an upgrade).

Anecdotal evidence on this forum suggests that some hotels will recognize the Platinum Elite guest and provide those benefits, while other hotels won't.

In short, don't count on Platinum Elite benefits, but ask -- and you might receive.