Wheelchair transport to the parks and 'disabled' rooms will be good most everywhere at WDW. Disney is fully complient with ADA and ahead of it in some respects!
I think your choice of Hotel should be based on your favourite parks - in other words, ignore disability access when making your choice.
I almost always stay at the Boardwalk because it has good access to my two favourite parks Epcot & MGM, good restaurants nearby.
I'm getting too old to enjoy Magic Kingdom! so the 'monorail' hotels don't appeal so much.
One factor no-one else has mentioned is access to the hotel swimming pools. Most hotels will have regular pool steps. If your friend cannot climb steps she needs a hotel like Beach/Yacht club and Wilderness Lodge which have what I call 'bump' steps which allow you to bump yourself out of the water one step at a time on your backside until you are at wheelchair seat level.
Some hotels such as Animal Kingdom Lodge, Polynesian and Grand Floridian have 'zero entrty level' pools that slope up to the surface like a beach. They have special waterproof wheelchairs on free loan so you can wheel your friend right into the water.
Your friend should consider renting a
scooter for the duration of your stay. The average visitor is said to walk about seven miles in a day ther - that is av long way to push a wheelchair. Disney transportation is scooter friendly.
Andrew