What does your friend have to say about it? I think she is the one to be on this forum, involved in the planning. What I can say is that if by the ,"first seven days" you mean SJPP onwards you are choosing to start with a very hard day, but that you could have have a long glide downhill by missing out Pamplona and going direct to La Reina.
Your friend might be interested in using an e-bike. If so, they can be hired. E-trikes are a whole other question. Rental is nearly impossible, and transport by train or bus the same. I have got one myself, and I will tell you now that while I love it, there are difficulties which don't arise with a two wheel vehicle.
One other point. Some walking and some cycling will be difficult to synchronise. I've walked and cycled Caminos, so I'm not coming to this discussion with any bias.
I honestly think that you could have a better chance of making this work with a support vehicle, and all of you cycling or all of you walking, with everyone having one day driving. That way you could transport packs without having to decide too much in advance where you will stay, and you would have more flexibility about accommodation.
Where do you all live? Do you have a long journey before you start? How will you return home?
This isn't something you can decide without the participation of the person with the disability, so please ask her if she would like to post here. I'm sure many people have experience they can share that would help if you could give us a little more information about your plans.