A lot will depend on both affordability and which parks will be primarily attended.
My first choice would be the Contemporary Tower. Everything, including the monorail, is just an elevator ride away. Also she can easily get to Magic Kingdom or Epcot by monorail.
Second choice would be Yacht or Beach Club, again, everything is just an elevator ride away. Here she could use a boat to Epcot or the Studio.
Boardwalk also uses a boat for Epcot and Studio, but to get to any of the restaurants she would have to go outside.
The Polynesian and Grand FLoridia have monorail access, but with the exception of some concierge rooms, everything there is in building other than where the restaurants and shops and front desk are.
Wilderness Lodge and Animal Kingdom Lodge have inside corridors and elevator access to all facilities, but bus transportation is needed for all the parks.
And the moderates and values all have rooms in buildings away from the rerstaurants, etc., and require bus transportation everywhere.