My mother also has MS (EDSS 9.0). We have had good rooms on Princess ships. You can find my photos of our cabin on the Island Princess (we have done this twice round-trip from LA to Hawaii), which not only is very accessible but accomodates 3, which we need. This cabin is right next to the ship's library, which is a good place to sit, read and look at the view.
You will see our travel lift and shower/commode chair in some of the photos.
http://www.cruisemates.com/gallery/m...bbc8a9036b1af7