They need to wait and see what happens with this latest relapse.
Janesy put a link to an interview with Dr [name removed by Moderator] from Russia which was really interesting. But one thing was highlighted for me. Stem cell transplantation can stop the disease process, prevent relapses and progression (if you are lucky, reading other accounts).
But it cannot reverse nerve damage. He said he did HSCT on someone who was SP and 6.5 on the EDSS. There was no further progression, so the stem cell transplant was a success, but the patient remains at 6.5.
So the damage that is being done to your sister could result in permanent damage, or it might result in complete remission from the relapse.
Following my major relapse 6 years ago, I had a lot of remission. But not complete. And the progression that has followed has left me SP with an EDSS of 7. So if I were to have HSCT, I would still be as disabled as I am today. I may not get worse, but even with the very best outcome, I wouldn’t get back what I have lost.
I really do hope that the plasma exchange actually does result in complete remission for your sister. And it’s possible. In which case, maybe she could get onto a trial here in the U.K. rather than use up all their assets for treatment abroad. I cannot imagine a better candidate for a trial because she started with having had only mild relapses before this last few months.