I've had hit or miss with this. At the Jamaica Hilton, I tried to get my wife a reservation on my name with her added on, but they wouldn't buy it (though my wife did get a nice fruit plate in the room and breakfast every day for my diamond status -- no points, though).
But last week, she stayed at a DT in Charlotte and she got the free breakfast, an upgrade, and I got the points.
So I'd go for it.