My dad had GBS about 20 years ago.
He had a very severe case and there's no nice way to say, it was awful and an extremely rough situation but he DID recover as most do (more on that below).
I have no idea the severity of her situation but it can range from a mild case to full blown paralysis like what my dad experienced and was very similar to what Gunsmith related above.
The one thing to remember and please make sure she understands this is that it IS something that people recover from, with severe cases it is probably the most awful thing someone can get that they actually recover from but the bottom line is that they DO recover and almost always go back to a fully or near fully-functioning state. There IS a light at the end of the tunnel.
It's a bizarre condition where something (usually an infection, and yes, often vaccines) triggers the body to attack the myelin that insulates your nerves. Once they break down enough, your nerve signals begin shorting out and you lose more and more nervous system function.
However long this goes on for and how much damage is done determines the severity and in any case, recovery is quite slow as the myelin does regenerate but does so very slowly.
I'm not familiar with what the person said above about versions from the virus being "reversible" but hopefully that is the case and doctors are on top of it.
I would strongly encourage them to look into plasmapherisis and IVIG. I had to fight my dad's doctor badly about most of this stuff and almost took his head off a couple of times.
I wish I knew then what I knew now but I would also have done more to make sure he was provided the proper nutrients (and possibly PEDs) to help maximize the regeneration of myelin during recovery.
It's been awhile since I thought about GBS so if I think of anything else I will add it.
Please do not hesitate to PM me id needed!