That's a very distressing situation.
I have not heard of a case like this, but one possibility that comes to mind is
Guillain-Barré Syndrome (GBS), which can cause paralysis after a viral or bacterial infection. A neurologist may be best qualified to recognize GBS, if that's indeed what it is. I found an
old paper documenting a GBS diagnosis after a transplant. Ironically, transplants can offer a cure for some kinds of paralysis.
Treatment for your friend requires a team approach and will be tough because of the transplant recovery also in progress.
A family member or a close friend like you needs to have your friend's permission to get details directly from the doctors, in order to help her navigate this scary path. She can't help herself very well so she needs people to learn what's going on, talk to her, comfort her, and advocate for her.
I hope you can get some answers and things turn around soon. If you keep up posted perhaps we can be of further help.