We picked up my MIL about 2 months ago at DFW, it was her first time to use her Tourist Visa, She speaks limited English. She is still in USA, headed back home this Sunday.
All they asked her was where she was staying and my wife had already provided our address, and how many pieces of luggage she has, She had one.
You can give her anything you want that makes you feel better, I think it's a waste of proving a letter saying you will provide lodging, I would think most parents on a tourist, that the child would be providing lodging and taking care of all thier expenses while in USA, and CBP would assume that.
They had asked my MIL who was paying for her trip when she did her visa interview, which she said we (Wife/Me) would do that.