Hi,
I think all the advice already given is brilliant. Yes, it would be a pilgrimage as Syates says, why not? A pilgrim is a person in motion, traveling landscapes sometimes unknown to them both externally and internally. I know there are rules regarding qualification for a Compostella by walking or riding, but this could be investigated.
But as a personal pilgrimage, the style should be set by her own needs and limitations. I like the idea of travelling by car and making pilgrimage to sites along the way. You could take a wheelchair which she could use as support to walk for awhile and when she tired she could be helped along. There are so many wonderful stretches of the Camino where it could be a lovely experience. AlwynWellington offers great advice above. Preplan with support. I am sure there will be many offers of help from other pilgrims.
Already people don't walk the entire distance and some do it by bike or horse....remember our footsteps may write our intent and prayer into the Caminos earth, but it is our heart that He will read.
I have attached a link below, not because i expect you to emulate this, but towards the end there is a wonderful example of community spirit that the Camino fosters and which I am sure would avail itself to you. The second clip is from the Six Ways to Santiago documentary and shows just how some adapt. Again i am not suggesting horse and carriage...just trying to encourage you with stories of others who make their camino..
Just do it! Grab a friend, hire a car and go walk when she can, ride when she can't. Buen Camino