|Liam and Lucy are lifelong friends, and he provides her with real help.|
I have a better idea: Pair the cat with a friend.
When I brought Lucy home, I was terrified that something horrible would happen to her and that she'd never find her way around. What she did, that first day, was yell her fool head off until Liam (the pug) ran over to her. Then, she simply pressed her body into his and followed him as he walked. If she got lost, she yelled some more and he came running. In about two days, she had my condo all mapped out.
When I moved into this much larger house (which has a big set of stairs, by the way), Lucy once again called on Liam to help her with mapping. She followed at his heels as he walked, and she cried out for help if she felt lost. She was the first of my three cats to come downstairs, the first to eat and the first to find the cat box. She felt secure because she knew Liam would bail her out if something went wrong.
These two have a very special bond that I think is very touching, but perhaps not rare. There are many, many stories of animals helping others in their community, especially if those other animals are somehow maimed or disfigured. Allowing your resident animals to assist a blind animal may be the best step you can take. Isolating your blind animal could mean your residents will never truly accept that blind animal, and your blind animal will never really have the full life it deserves.
Blind cats are truly amazing animals, capable of overcoming the disability with remarkable speed and grace. Let your blind cat surprise you. Use baby gates to keep your cat from falling down the stairs, of course, but don't be afraid to let her explore the house at her own speed with the help of her friends.