I suspect that the OP doesn't want to "share" the room during the time the OP is there, nor does the OP want the "friend" to have keycards for the OP's room during that time. The "friend" will be in a separate room at first.

However, the OP would ultimately be responsible for any damage the person does to the room (have a wild party and trash it?) as well as anything (multiple bottles of vintage champagne from room service? Big dinners for everyone in the hotel's restaurant?) charged to the room. Is it worth taking the risk?