GBS is NOT contagious–you cannot pass it on to people around you (except possibly by transfusion of the antibody in a blood product). You can pass on stomach flus.
The most likely explanation for your wife is that she is tired already (from worry and stress about you and the whole situation and probably from trying to do a lot to make things as if normal for your family). If someone has a bad stomach flu, they can lose a lot of salts and this can affect the nervous system. If possible, both of you try to drink some GadorAide or similar sports drink or even better, one of these diluted into half (which makes a better electrolyte replenishing beverage). Be careful of artificial sweeteners or lots of sugars when having bad diarrhea. Many people need to be careful of milk after diarrhea because you can get a transient lactose intolerance. Both of you rest. If either of you are throwing up, try sips of GatorAide very slowly. Or make popsickles. You have to eat popsickles slowly and it is a good excuse for a popsickle as an adult, no?
WithHope for cure of these diseases