I think you can call and add a name to the reservation. Last Spring, I made a reservation for my wife at a Hilton property and planned on traveling with her. The reservation was in my name, and due to work changes, I couldn't go. The hotel was a nice beach property and ended up full. So I was in the same boat as you. I called reservations and added her name to the reservation. She didn't have any issues at all with that reservation.

(Though she was a bit preturbed because I ended up still getting the points and the night rather than her even though I wasn't there. She had more stays at Hiltons, so it would have been better for her to get the points/nights. )