additional thoughts

I just have a few things to add to the suggestions you already have based on caring for my mother when she could no longer walk and on my experiences (thankfully less severe with GBS). It is important for people to still feel independent. It is ALSO important for you and your husband to have some time alone and time away. Sometimes it is assumed by the rest of the family that you will do it all (because you are a nurse or a caring person or young–or whatever excuses there are). Anyway, these are my suggestions. Think early about things that permit independence such as a bedside commode or shower/tub stool. If it is hard for her to get up out of bed, think about a hospital bed with rails to help. Think about a table or stack of small shelves for important things that people would get up and get if they could (kleenex, pens/pencils and paper, books, water, nail file, phone and phone list of important numbers, clock, lipstick, etc).
Encourage her family and friends to come visit. It will help your MIL and you by making life a tiny bit more normal. One of the hard things for me was that I was more isolated after GBS and had no energy to go other places. Suggest that people bring a “picnic” lunch of favorites for her or when she is better take you out in a wheelchair for brief visits out of the house. It is hard because with GBS, life changes so suddenly, there is little time to adjust to it.
One of the hard things for my Dad who was primary caregiver for my mother was the constantness of it all and that he had little time away since we all live far away. It is hard to take care of ANYONE 24/7 even if you are a very caring person. It is worth thinking now about options for time away just to refresh you and your husbands batteries. If you have the only accessible house in the family, maybe someone can come and stay with your MIL a day or two, while you have a little respite time. I understand your MIL is a wonderful person, but it is a change in life that all of you have to adjust to having. I know I wanted as much independence as I could have after getting ill. You can help her and help set the stage for other to help as well, by thinking ahead a little and keep it kind by emphasizing that it is for life-normalization and to help her not get bored and depressed. Friends and family and variety and things to look forward to doing are the best medicine for that.
WithHope for a cure of these diseases